2024

Jump to: 2023, 2022, 2021, 2020

13 pages, 3884 KiB

Open AccessArticle

Micron-Sized Thiol-Functional Polysilsesquioxane Microspheres with Open and Interconnected Macropores: Preparation, Characterization and Formation Mechanism

by Lu Han, Zhenyu Nie, Rongsheng Gao, Zhengyang Jiang and Chengyou Kan

Molecules 2024, 29(6), 1204; https://doi.org/10.3390/molecules29061204 - 08 Mar 2024

Viewed by 419

Abstract

Polysilsesquioxane (PSQ) microspheres have shown promise in many fields, but previous studies about porous PSQ microspheres are scarce. Herein, we fabricated novel micron-sized thiol-functional polysilsesquioxane (TMPSQ) microspheres with open and interconnected macropores by combining inverse suspension polymerization with two-step sol–gel and polymerization-induced phase [...] Read more.

Polysilsesquioxane (PSQ) microspheres have shown promise in many fields, but previous studies about porous PSQ microspheres are scarce. Herein, we fabricated novel micron-sized thiol-functional polysilsesquioxane (TMPSQ) microspheres with open and interconnected macropores by combining inverse suspension polymerization with two-step sol–gel and polymerization-induced phase separation processes, without using phase-separation-promoting additives or sacrificial templates. The chemical composition of the TMPSQ microspheres was confirmed using FTIR and Raman spectroscopy. The morphology of the TMPSQ microspheres was characterized using SEM and TEM. TGA was employed to test the thermal stability of the TMPSQ microspheres. Mercury intrusion porosimetry and nitrogen adsorption–desorption tests were performed to investigate the pore structure of the TMPSQ microspheres. The results showed that the TMPSQ microspheres had open and interconnected macropores with a pore size of 839 nm, and the total porosity and intraparticle porosity reached 70.54% and 43.21%, respectively. The mechanism of porous generation was proposed based on the morphological evolution observed using optical microscopy. The macropores were formed through the following four steps: phase separation (spinodal decomposition), coarsening, gelation, and evaporation of the solvent. The macropores can facilitate the rapid mass transfer between the outer and inner spaces of the TMPSQ microspheres. The TMPSQ microspheres are promising in various fields, such as catalyst supports and adsorbents. Full article

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2023

Jump to: 2024, 2022, 2021, 2020

35 pages, 6320 KiB

Open AccessReview

An Overview of Heterogeneous Catalysts Based on Hypercrosslinked Polystyrene for the Synthesis and Transformation of Platform Chemicals Derived from Biomass

by Oleg Manaenkov, Linda Nikoshvili, Alexey Bykov, Olga Kislitsa, Maxim Grigoriev, Mikhail Sulman, Valentina Matveeva and Lioubov Kiwi-Minsker

Molecules 2023, 28(24), 8126; https://doi.org/10.3390/molecules28248126 - 15 Dec 2023

Viewed by 730

Abstract

Platform chemicals, also known as chemical building blocks, are substances that serve as starting materials for the synthesis of various value-added products, which find a wide range of applications. These chemicals are the key ingredients for many fine and specialty chemicals. Most of [...] Read more.

Platform chemicals, also known as chemical building blocks, are substances that serve as starting materials for the synthesis of various value-added products, which find a wide range of applications. These chemicals are the key ingredients for many fine and specialty chemicals. Most of the transformations of platform chemicals are catalytic processes, which should meet the requirements of sustainable chemistry: to be not toxic for humans, to be safe for the environment, and to allow multiple reuses of catalytic materials. This paper presents an overview of a new class of heterogeneous catalysts based on nanoparticles of catalytically active metals stabilized by a polymer matrix of hypercrosslinked polystyrene (HPS). This polymeric support is characterized by hierarchical porosity (including meso- and macropores along with micropores), which is important both for the formation of metal nanoparticles and for efficient mass transfer of reactants. The influence of key parameters such as the morphology of nanoparticles (bimetallic versus monometallic) and the presence of functional groups in the polymer matrix on the catalytic properties is considered. Emphasis is placed on the use of this class of heterogeneous catalysts for the conversion of plant polysaccharides into polyols (sorbitol, mannitol, and glycols), hydrogenation of levulinic acid, furfural, oxidation of disaccharides, and some other reactions that might be useful for large-scale industrial processes that aim to be sustainable. Some challenges related to the use of HPS-based catalysts are addressed and multiple perspectives are discussed. Full article

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17 pages, 2953 KiB

Open AccessArticle

Synthesis and Characterization of Proton-Conducting Composites Prepared by Introducing Imidazole or 1,2,4-Triazole into AlPO-5 and SAPO-5 Molecular Sieves

by Adam Ostrowski, Aldona Jankowska, Agata Tabero, Ewa Janiszewska and Stanisław Kowalak

Molecules 2023, 28(21), 7312; https://doi.org/10.3390/molecules28217312 - 28 Oct 2023

Viewed by 752

Abstract

The present work concerns proton-conducting composites obtained by replacing the water molecules present in aluminophosphate and silicoaluminophosphate AFI-type molecular sieves (AlPO-5 and SAPO-5) with azole molecules (imidazole or 1,2,4-triazole). Both the introduction of azoles and the generation of Brønsted acid centers by isomorphous [...] Read more.

The present work concerns proton-conducting composites obtained by replacing the water molecules present in aluminophosphate and silicoaluminophosphate AFI-type molecular sieves (AlPO-5 and SAPO-5) with azole molecules (imidazole or 1,2,4-triazole). Both the introduction of azoles and the generation of Brønsted acid centers by isomorphous substitution in aluminophosphate materials were aimed at improving the proton conductivity of the materials and its stability. In the presented study, AlPO-5 and several SAPO-5 materials differing in silicon content were synthesized. The obtained porous matrices were studied using PXRD, low-temperature nitrogen sorption, TPD-NH₃, FTIR, and SEM. The proton conductivity of composites was measured using impedance spectroscopy. The results show that the increase in silicon content of the porous matrices is accompanied by an increase in their acidity. However, this does not translate into an increase in the conductivity of the azole composites. Triazole composites show lower conductivity and significantly higher activation energies than imidazole composites; however, most triazole composites show much higher stability. The different conductivity values for imidazole and triazole composites may be due to differences in chemical properties of the azoles. Full article

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27 pages, 1430 KiB

Open AccessReview

Sol–Gel Technologies to Obtain Advanced Bioceramics for Dental Therapeutics

by Xiaozhe Song, Juan J. Segura-Egea and Aránzazu Díaz-Cuenca

Molecules 2023, 28(19), 6967; https://doi.org/10.3390/molecules28196967 - 07 Oct 2023

Cited by 4 | Viewed by 1727

Abstract

The aim of this work is to review the application of bioceramic materials in the context of current regenerative dentistry therapies, focusing on the latest advances in the synthesis of advanced materials using the sol–gel methodology. Chemical synthesis, processing and therapeutic possibilities are [...] Read more.

The aim of this work is to review the application of bioceramic materials in the context of current regenerative dentistry therapies, focusing on the latest advances in the synthesis of advanced materials using the sol–gel methodology. Chemical synthesis, processing and therapeutic possibilities are discussed in a structured way, according to the three main types of ceramic materials used in regenerative dentistry: bioactive glasses and glass ceramics, calcium phosphates and calcium silicates. The morphology and chemical composition of these bioceramics play a crucial role in their biological properties and effectiveness in dental therapeutics. The goal is to understand their chemical, surface, mechanical and biological properties better and develop strategies to control their pore structure, shape, size and compositions. Over the past decades, bioceramic materials have provided excellent results in a wide variety of clinical applications related to hard tissue repair and regeneration. Characteristics, such as their similarity to the chemical composition of the mineral phase of bones and teeth, as well as the possibilities offered by the advances in nanotechnology, are driving the development of new biomimetic materials that are required in regenerative dentistry. The sol–gel technique is a method for producing synthetic bioceramics with high purity and homogeneity at the molecular scale and to control the surfaces, interfaces and porosity at the nanometric scale. The intrinsic nanoporosity of materials produced by the sol–gel technique correlates with the high specific surface area, reactivity and bioactivity of advanced bioceramics. Full article

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16 pages, 35205 KiB

Open AccessArticle

Dendritic Mesoporous Organosilica Nanoparticles with Photosensitizers for Cell Imaging, siRNA Delivery and Protein Loading

by Haneen Omar, Sara Jakimoska, Julia Guillot, Edreese Alsharaeh, Clarence Charnay, Frédérique Cunin, Aurélie Bessière, Jean-Olivier Durand, Laurence Raehm, Laure Lichon, Mélanie Onofre and Magali Gary-Bobo

Molecules 2023, 28(14), 5335; https://doi.org/10.3390/molecules28145335 - 11 Jul 2023

Viewed by 1162

Abstract

Dendritic mesoporous organosilica nanoparticles (DMON) are a new class of biodegradable nanoparticles suitable for biomolecule delivery. We studied the photochemical internalization (PCI) and photodynamic therapy (PDT) of DMON to investigate new ways for DMON to escape from the endosomes-lysosomes and deliver biomolecules into [...] Read more.

Dendritic mesoporous organosilica nanoparticles (DMON) are a new class of biodegradable nanoparticles suitable for biomolecule delivery. We studied the photochemical internalization (PCI) and photodynamic therapy (PDT) of DMON to investigate new ways for DMON to escape from the endosomes-lysosomes and deliver biomolecules into the cytoplasm of cells. We added photosensitizers in the framework of DMON and found that DMON were loaded with siRNA or FVIII factor protein. We made four formulations with four different photosensitizers. The photosensitizers allowed us to perform imaging of DMON in cancer cells, but the presence of the tetrasulfide bond in the framework of DMON quenched the formation of singlet oxygen. Fortunately, one formulation allowed us to efficiently deliver proapoptotic siRNA in MCF-7 cancer cells leading to 31% of cancer cell death, without irradiation. As for FVIII protein, it was loaded in two formulations with drug-loading capacities (DLC) up to 25%. In conclusion, DMON are versatile nanoparticles capable of loading siRNA and delivering it into cancer cells, and also loading FVIII protein with good DLC. Due to the presence of tetrasulfide, it was not possible to perform PDT or PCI. Full article

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17 pages, 5308 KiB

Open AccessArticle

Carbon Adsorbents Obtained from Pistachio Nut Shells Used as Potential Ingredients of Drinking Water Filters

by Agata Wawrzyniak, Małgorzata Wiśniewska and Piotr Nowicki

Molecules 2023, 28(11), 4497; https://doi.org/10.3390/molecules28114497 - 01 Jun 2023

Cited by 4 | Viewed by 1545

Abstract

Water resources are increasingly degraded due to the discharge of waste generated in municipal, industrial and agricultural areas. Therefore, the search for new materials enabling the effective treatment of drinking water and sewage is currently of great interest. This paper deals with the [...] Read more.

Water resources are increasingly degraded due to the discharge of waste generated in municipal, industrial and agricultural areas. Therefore, the search for new materials enabling the effective treatment of drinking water and sewage is currently of great interest. This paper deals with the adsorption of organic and inorganic pollutants on the surface of carbonaceous adsorbents prepared by thermochemical conversion of common pistachio nut shells. The influence of the direct physical activation with CO₂ and chemical activation with H₃PO₄ on parameters, such as elemental composition, textural parameters, acidic–basic character of the surface as well as electrokinetic properties of the prepared carbonaceous materials was checked. The suitability of the activated biocarbons prepared as the adsorbents of iodine, methylene blue and poly(acrylic acid) from the aqueous solutions was estimated. The sample obtained via chemical activation of the precursor turned out to be much more effective in terms of all the tested pollutants adsorption. Its maximum sorption capacity toward iodine was 1059 mg/g, whereas in relation to methylene blue and poly(acrylic acid) 183.1 mg/g and 207.9 mg/g was achieved, respectively. For both carbonaceous materials, a better fit to the experimental data was achieved with a Langmuir isotherm than a Freundlich one. It has also been shown that the efficiency of organic dye, and especially anionic polymer adsorption from aqueous solutions, is significantly affected by solution pH and temperature of the adsorbate–adsorbent system. Full article

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14 pages, 4247 KiB

Open AccessArticle

Novel Carbonaceous Adsorbents Prepared from Glycerin Waste and Dopamine for Gas Separation

by Mary Batista, Renato Carvalho, Moisés L. Pinto and João Pires

Molecules 2023, 28(10), 4071; https://doi.org/10.3390/molecules28104071 - 13 May 2023

Viewed by 1196

Abstract

Glycerin, a low-valued waste from biodiesel production, and dopamine were used as precursors for adsorbent materials. The study is centered on the preparation and application of microporous activated carbon as adsorbent materials in the separation of ethane/ethylene and of gases that are natural [...] Read more.

Glycerin, a low-valued waste from biodiesel production, and dopamine were used as precursors for adsorbent materials. The study is centered on the preparation and application of microporous activated carbon as adsorbent materials in the separation of ethane/ethylene and of gases that are natural gas or landfill gas components (ethane/methane and carbon dioxide/methane). The activated carbons were produced by the following sequence reactions: facile carbonization of a glycerin/dopamine mixture and chemical activation. Dopamine allowed the introduction of nitrogenated groups that improved the selectivity of the separations. The activating agent was KOH, but its mass ratio was kept lower than one to improve the sustainability of the final materials. The solids were characterized by N₂ adsorption/desorption isotherms, SEM, FTIR spectroscopy, elemental analysis, and point of zero charges (pH_PZC). The order for adsorption of the different adsorbates (in mmolg⁻¹) on the most well performing material—Gdop0.75—is methane (2.5) < carbon dioxide (5.0) < ethylene (8.6) < ethane (8.9). Full article

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13 pages, 5322 KiB

Open AccessArticle

Reliability Characteristics of Metal-Insulator-Semiconductor Capacitors with Low-Dielectric-Constant Materials

by Yi-Lung Cheng, Wei-Fan Peng, Chi-Jia Huang, Giin-Shan Chen and Jau-Shiung Fang

Molecules 2023, 28(3), 1134; https://doi.org/10.3390/molecules28031134 - 23 Jan 2023

Cited by 1 | Viewed by 1594

Abstract

In this study, the reliability characteristics of metal-insulator-semiconductor (MIS) capacitor structures with low-dielectric-constant (low-k) materials have been investigated in terms of metal gate area and geometry and thickness of dielectric film effects. Two low-k materials, dense and porous low-k [...] Read more.

In this study, the reliability characteristics of metal-insulator-semiconductor (MIS) capacitor structures with low-dielectric-constant (low-k) materials have been investigated in terms of metal gate area and geometry and thickness of dielectric film effects. Two low-k materials, dense and porous low-k films, were used. Experimental results indicated that the porous low-k films had shorter breakdown times, lower Weibull slope parameters and electric field acceleration factors, and weaker thickness-dependence breakdowns compared to the dense low-k films. Additionally, a larger derivation in dielectric breakdown projection model and a single Weilbull plot of the breakdown time distributions from various areas merging was observed. This study also pointed out that the porous low-k film in the irregular-shaped metal gate MIS capacitor had a larger dielectric breakdown time than that in the square- and circle-shaped samples, which violates the trend of the sustained electric field. As a result, another breakdown mechanism exists in the irregular-shaped sample, which is required to explore in the future work. Full article

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2022

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11 pages, 2402 KiB

Open AccessArticle

The Kinetics of Formation of Microporous Polytriazine in Diphenyl Sulfone

by Andrey Galukhin, Ilya Nikolaev, Roman Nosov and Sergey Vyazovkin

Molecules 2022, 27(11), 3605; https://doi.org/10.3390/molecules27113605 - 03 Jun 2022

Cited by 4 | Viewed by 1323

Abstract

This study highlights the value of nonisothermal kinetic methods in selecting temperature conditions for the isothermal preparation of microporous polymeric materials. A dicyanate ester is synthesized and the kinetics of its polymerization in diphenyl sulfone are studied by calorimetry under nonisothermal conditions. The [...] Read more.

This study highlights the value of nonisothermal kinetic methods in selecting temperature conditions for the isothermal preparation of microporous polymeric materials. A dicyanate ester is synthesized and the kinetics of its polymerization in diphenyl sulfone are studied by calorimetry under nonisothermal conditions. The kinetics are analyzed by a model-based approach, using the Kamal model, as well as by a model-free approach, using an advanced isoconversional method. Both approaches correctly predict the time to completion of polymerization at a given temperature. The material prepared independently at the predicted temperature is characterized by electron microscopy and CO₂ adsorption measurements and is confirmed to possess a microporous structure with a multimodal distribution of micropores with two major maxima at ~0.5 and 0.8 nm. Full article

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2021

Jump to: 2024, 2023, 2022, 2020

19 pages, 27820 KiB

Open AccessArticle

Hierarchical Zeolites as Catalysts for Biodiesel Production from Waste Frying Oils to Overcome Mass Transfer Limitations

by Elyssa G. Fawaz, Darine A. Salam, Severinne S. Rigolet and T. Jean Daou

Molecules 2021, 26(16), 4879; https://doi.org/10.3390/molecules26164879 - 12 Aug 2021

Cited by 13 | Viewed by 2128

Abstract

Hierarchical crystals with short diffusion path, conventional microcrystals and nanocrystals of ZSM-5 zeolites were used for biodiesel production from waste frying oils and were assessed for their catalytic activity in regard to their pore structure and acidic properties. Produced zeolites were characterized using [...] Read more.

Hierarchical crystals with short diffusion path, conventional microcrystals and nanocrystals of ZSM-5 zeolites were used for biodiesel production from waste frying oils and were assessed for their catalytic activity in regard to their pore structure and acidic properties. Produced zeolites were characterized using XRD, nitrogen adsorption–desorption, SEM, TEM, X-ray fluorescence, and FTIR. Pore size effect on molecular diffusion limitation was assessed by Thiele modulus calculations and turnover frequencies (TOF) were used to discuss the correlation between acidic character and catalytic performance of the zeolites. Owing to the enhanced accessibility and mass transfer of triglycerides and free fatty acids to the elemental active zeolitic structure, the catalytic performance of nanosponge and nanosheet hierarchical zeolites was the highest. A maximum yield of 48.29% was reached for the transesterification of waste frying oils (WFOs) using HZSM-5 nanosheets at 12:1 methanol to WFOs molar ratio, 180 °C, 10 wt % catalyst loading, and 4 h reaction time. Although HZSM-5 nanosponges achieved high conversions, these more hydrophilic zeolites did not function according to their entire acidic strength in comparison to HZSM-5 nanosheets. NSh-HZSM5 catalytic performance was still high after 4 consecutive cycles as a result of the zeolite regeneration. Full article

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26 pages, 51971 KiB

Open AccessArticle

Zeolite-Polymer Composite Materials as Water Scavenger

by Zakaria Tahraoui, Habiba Nouali, Claire Marichal, Patrice Forler, Julien Klein and T. Jean Daou

Molecules 2021, 26(16), 4815; https://doi.org/10.3390/molecules26164815 - 09 Aug 2021

Cited by 6 | Viewed by 2850

Abstract

The influence of the charge compensating cation nature (Na⁺, Mg²⁺) on the water adsorption properties of LTA-type zeolites used as filler in composite materials (zeolite/polymers) was investigated. Large scale cation exchanges were performed on zeolite powder at 80 °C [...] Read more.

The influence of the charge compensating cation nature (Na⁺, Mg²⁺) on the water adsorption properties of LTA-type zeolites used as filler in composite materials (zeolite/polymers) was investigated. Large scale cation exchanges were performed on zeolite powder at 80 °C for 2 h using 1 M magnesium chloride (MgCl₂) aqueous solutions. XRF, ICP, and EDX analyses indicate a successful cationic exchange process without the modification of the zeolite structure as shown by XRD and solid-state NMR analyses. Composite materials (granulates and molded parts) were manufactured using to extrusion and injection processes. In the case of MgA zeolite, nitrogen adsorption–desorption experiments allowed us to measure a microporous volume, unlike NaA zeolite, which is non-porous to nitrogen probe molecule. SEM and EDX analyses highlighted the homogeneous distribution of zeolite crystals into the polymer matrix. Water adsorption capacities confirmed that the trends observed in the zeolite powder samples are preserved after dragging zeolites into composite formulations. Granulates and molded parts composite samples containing the magnesium exchanged zeolite showed an increase of their water adsorption capacity up to +27% in comparison to composite samples containing the non-exchanged zeolite. The MgA composite is more promising for water decontamination applications due to its higher water adsorption properties than the NaA composite. Full article

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14 pages, 1829 KiB

Open AccessArticle

The Properties of Cu Ions in Zeolites CuY Studied by IR Spectroscopy

by Jerzy Podobiński, Mariusz Gackowski, Grzegorz Mordarski, Katarzyna Samson, Michał Śliwa, Dorota Rutkowska-Zbik and Jerzy Datka

Molecules 2021, 26(15), 4686; https://doi.org/10.3390/molecules26154686 - 03 Aug 2021

Cited by 1 | Viewed by 1969

Abstract

The properties of both Cu²⁺ and Cu⁺ ions in zeolite CuY were followed with NO and CO as probe molecules. Cu²⁺ was found to be located in S_II, S_II*, and S_III sites, whereas Cu⁺ [...] Read more.

The properties of both Cu²⁺ and Cu⁺ ions in zeolite CuY were followed with NO and CO as probe molecules. Cu²⁺ was found to be located in S_II, S_II*, and S_III sites, whereas Cu⁺ was found in S_II and S_II* sites. The fine analysis of the spectra of Cu²⁺-NO and Cu⁺-CO adducts suggests that both in S_II and in S_II* sites two kinds of Cu cations exist. They differ in the positive charge, which may be related to the varying numbers of AlO₄⁻ in close proximity. The experiments of NO and CO adsorption and desorption evidenced that both Cu²⁺ and Cu⁺ sites of highest positive charge bind probe molecules most strongly but activate them to a lesser extent than the Cu sites of lowest positive charge. The experiments of reduction with hydrogen evidenced that the Cu ions of higher positive charge are first reduced by hydrogen. On the other hand, Cu sites of the lowest positive charge are first oxidized by oxygen. The experiments with CuNaY zeolites of various Cu contents suggest that the first introduced Cu (at low Cu contents) created Cu⁺, which was the most neutralized by framework oxygens. Such Cu cations are the most stabilized by framework oxygens. Full article

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14 pages, 15016 KiB

Open AccessArticle

Synthesis of Hierarchical MOR-Type Zeolites with Improved Catalytic Properties

by Zeinab Mcheik, Ludovic Pinard, Joumana Toufaily, Tayssir Hamieh and T. Jean Daou

Molecules 2021, 26(15), 4508; https://doi.org/10.3390/molecules26154508 - 27 Jul 2021

Cited by 4 | Viewed by 2043

Abstract

Hierarchical MOR-type zeolites were synthesized in the presence of hexadecyltrimethylammonium bromide (CTAB) as a porogen agent. XRD proved that the concentration of CTAB in the synthesis medium plays an essential role in forming pure hierarchical MOR-type material. Above a CTAB concentration of 0.04 [...] Read more.

Hierarchical MOR-type zeolites were synthesized in the presence of hexadecyltrimethylammonium bromide (CTAB) as a porogen agent. XRD proved that the concentration of CTAB in the synthesis medium plays an essential role in forming pure hierarchical MOR-type material. Above a CTAB concentration of 0.04 mol·L⁻¹, amorphous materials are observed. These hierarchical mordenite possess a higher porous volume compared to its counterpart conventional micrometer crystals. Nitrogen sorption showed the presence of mesoporosity for all mordenite samples synthesized in the presence of CTAB. The creation of mesopores due to the presence of CTAB in the synthesis medium does not occur at the expense of zeolite micropores. In addition, mesoporous volume and BET surface seem to increase upon the increase of CTAB concentration in the synthesis medium. The Si/Al ratio of the zeolite framework can be increased from 5.5 to 9.1 by halving the aluminum content present in the synthesis gel. These synthesized hierarchical MOR-type zeolites possess an improved catalytic activity for n-hexane cracking compared to large zeolite crystals obtained in the absence of CTAB. Full article

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14 pages, 3207 KiB

Open AccessArticle

Study of Mono- and Bimetallic Fe and Mn Oxide-Supported Clinoptilolite for Improved Pb(II) Removal

by Eva Chmielewská, Wlodzimierz Tylus and Marek Bujdoš

Molecules 2021, 26(14), 4143; https://doi.org/10.3390/molecules26144143 - 07 Jul 2021

Cited by 8 | Viewed by 1663

Abstract

A cost-effective, iron- and manganese-oxide-supported clinoptilolite-based rock was prepared. Based on its nanoporous structure, it worked as a nanoreactor, thereby providing enhanced functionalities. The mono- and bimetallic Fe- and Mn-oxide-supported clinoptilolite was thoroughly characterized with thermoanalytical FT-IR, XRD, SEM, and XPS spectroscopy. All [...] Read more.

A cost-effective, iron- and manganese-oxide-supported clinoptilolite-based rock was prepared. Based on its nanoporous structure, it worked as a nanoreactor, thereby providing enhanced functionalities. The mono- and bimetallic Fe- and Mn-oxide-supported clinoptilolite was thoroughly characterized with thermoanalytical FT-IR, XRD, SEM, and XPS spectroscopy. All the spectral procedures that were used confirmed the occurrence of a new MnO₂ phase (predominantly birnessite), including mostly amorphous iron oxi(hydr)oxide (FeO(OH)) species on the surface of the above-synthesized adsorbents. The synthesized products validated a considerably higher adsorption capacity toward Pb(II) pollutants compared to the natural clinoptilolite. The following order of a(max) toward Pb(II) was found: MnOx-zeolite (202.1 mg/g) > FeO(OH)-MnOx-zeolite (101.3 mg/g) > FeO(OH)-zeolite (80 mg/g) > natural zeolite (54.9 mg/g). The adsorption equilibrium data were analyzed by the two-parameter empirical isotherm models Langmuir, Freundlich, and BET as well as the three-parameter Redlich–Peterson isotherm. Full article

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9 pages, 2403 KiB

Open AccessArticle

Offretite Zeolite Single Crystals Synthesized by Amphiphile-Templating Approach

by Eng-Poh Ng, Nur Hidayahni Ahmad, Fitri Khoerunnisa, Svetlana Mintova, Tau Chuan Ling and T. Jean Daou

Molecules 2021, 26(8), 2238; https://doi.org/10.3390/molecules26082238 - 13 Apr 2021

Viewed by 1958

Abstract

Offretite zeolite synthesis in the presence of cetyltrimethylammonium bromide (CTABr) is reported. The offretite crystals were synthesized with a high crystallinity and hexagonal prismatic shape after only 72 h of hydrothermal treatment at 180 °C. The CTABr has dual-functions during the crystallization of [...] Read more.

Offretite zeolite synthesis in the presence of cetyltrimethylammonium bromide (CTABr) is reported. The offretite crystals were synthesized with a high crystallinity and hexagonal prismatic shape after only 72 h of hydrothermal treatment at 180 °C. The CTABr has dual-functions during the crystallization of offretite, viz. as structure-directing agent and as mesoporogen. The resulting offretite crystals, with a Si/Al ratio of 4.1, possess more acid sites than the conventional offretite due to their high crystallinity and hierarchical structure. The synthesized offretite is also more reactive than its conventional counterpart in the acylation of 2-methylfuran for biofuel production under non-microwave instant heating condition, giving 83.5% conversion with 100% selectivity to the desired product 2-acetyl-5-methylfuran. Hence, this amphiphile synthesis approach offers another cost-effective and alternative route for crystallizing zeolite materials that require expensive organic templates. Full article

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11 pages, 2856 KiB

Open AccessArticle

Preparation of High-Performance Activated Carbon from Coffee Grounds after Extraction of Bio-Oil

by Jie Ren, Nanwei Chen, Li Wan, Guojian Li, Tao Chen, Fan Yang and Shuiyu Sun

Molecules 2021, 26(2), 257; https://doi.org/10.3390/molecules26020257 - 06 Jan 2021

Cited by 4 | Viewed by 2487

Abstract

In this study, a new method for economical utilization of coffee grounds was developed and tested. The resulting materials were characterized by proximate and elemental analyses, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and N₂ adsorption–desorption at [...] Read more.

In this study, a new method for economical utilization of coffee grounds was developed and tested. The resulting materials were characterized by proximate and elemental analyses, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and N₂ adsorption–desorption at 77 K. The experimental data show bio-oil yields reaching 42.3%. The optimal activated carbon was obtained under vacuum pyrolysis self-activation at an operating temperature of 450 °C, an activation temperature of 600 °C, an activation time of 30 min, and an impregnation ratio with phosphoric acid of 150 wt.%. Under these conditions, the yield of activated carbon reached 27.4% with a BET surface area of 1420 m²·g⁻¹, an average pore size of 2.1 nm, a total pore volume of 0.747 cm³·g⁻¹, and a t-Plot micropore volume of 0.428 cm³·g⁻¹. In addition, the surface of activated carbon looked relatively rough, containing mesopores and micropores with large amounts of corrosion pits. Full article

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2020

Jump to: 2024, 2023, 2022, 2021

14 pages, 4873 KiB

Open AccessArticle

Migration, Crystallization and Dissolution Changes of Salt Solution with Color Rendering Property in Porous Quartz Materials

by Jing Zhao, Hongjie Luo and Xiao Huang

Molecules 2020, 25(23), 5708; https://doi.org/10.3390/molecules25235708 - 03 Dec 2020

Cited by 3 | Viewed by 1911

Abstract

In order to visually display the migration and crystallization process of salt solution in porous cultural relics, copper sulfate solution with color rendering property was selected to record the migration, crystallization and resolution of salt solution in simulated SiO₂ samples under different [...] Read more.

In order to visually display the migration and crystallization process of salt solution in porous cultural relics, copper sulfate solution with color rendering property was selected to record the migration, crystallization and resolution of salt solution in simulated SiO₂ samples under different environmental conditions in real time through high-resolution recording system, scanning electron microscope system, salt phase X-ray diffraction system, and so on. The results showed the migration of salt solution in porous samples was related to the structural characteristics of the porous samples, the migration rate of salt solution, the evaporation rate and the change frequency of crystallization–resolution, etc., in which the large pore size of the sample, the higher the concentration and the faster migration and evaporation rate of salt solution, the greater the change rate of the brine accumulation zone or salt crystallization zone in the different porous samples. During the humidification–drying cycles of rainfall, the higher the cycle frequency of humidification–drying was, the higher the drying temperature was, the more frequent the crystallization-analysis change of salt in the salt-bearing sample was, and the more extensive the distribution of salt crystal zone was. This is the first time to visualize the salt belt by simulating the changing process of a salt solution with a color rendering property in porous samples. This has scientific theoretical guidance for the study of the migration–crystallization changes of soluble salts contained in porous silicate cultural relics. The visibility analysis results of multilayer salt crystal belts can also provide the preliminary basis for further effective desalination of salt bearing cultural relics. Full article

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15 pages, 4172 KiB

Open AccessArticle

Pressureless and Low-Pressure Synthesis of Microporous Carbon Spheres Applied to CO₂ Adsorption

by Iwona Pełech, Daniel Sibera, Piotr Staciwa, Urszula Narkiewicz and Robert Cormia

Molecules 2020, 25(22), 5328; https://doi.org/10.3390/molecules25225328 - 15 Nov 2020

Cited by 11 | Viewed by 2133

Abstract

In this work, low-pressure synthesis of carbon spheres from resorcinol and formaldehyde using an autoclave is presented. The influence of reaction time and process temperature as well as the effect of potassium oxalate, an activator, on the morphology and CO₂ adsorption properties [...] Read more.

In this work, low-pressure synthesis of carbon spheres from resorcinol and formaldehyde using an autoclave is presented. The influence of reaction time and process temperature as well as the effect of potassium oxalate, an activator, on the morphology and CO₂ adsorption properties was studied. The properties of materials produced at pressureless (atmospheric) conditions were compared with those synthesized under higher pressures. The results of this work show that enhanced pressure treatment is not necessary to produce high-quality carbon spheres, and the morphology and porosity of the spheres produced without an activation step at pressureless conditions are not significantly different from those obtained at higher pressures. In addition, CO₂ uptake was not affected by elevated pressure synthesis. It was also demonstrated that addition of the activator (potassium oxalate) had much more effect on key properties than the applied pressure treatment. The use of potassium oxalate as an activator caused non-uniform size distribution of spherical particles. Simultaneously higher values of surface area and total pore volumes were reached. A pressure treatment of the carbon materials in the autoclave significantly enhanced the CO₂ uptake at 25 °C, but had no effect on it at 0 °C. Full article

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20 pages, 4422 KiB

Open AccessArticle

Tamoxifen Delivery System Based on PEGylated Magnetic MCM-41 Silica

by Margarita Popova, Neli Koseva, Ivalina Trendafilova, Hristina Lazarova, Violeta Mitova, Judith Mihály, Denitsa Momekova, Georgi Momekov, Iskra Z. Koleva, Hristiyan A. Aleksandrov, Georgi N. Vayssilov and Ágnes Szegedi

Molecules 2020, 25(21), 5129; https://doi.org/10.3390/molecules25215129 - 04 Nov 2020

Cited by 7 | Viewed by 2398

Abstract

Magnetic iron oxide containing MCM-41 silica (MM) with ~300 nm particle size was developed. The MM material before or after template removal was modified with NH₂- or COOH-groups and then grafted with PEG chains. The anticancer drug tamoxifen was loaded into [...] Read more.

Magnetic iron oxide containing MCM-41 silica (MM) with ~300 nm particle size was developed. The MM material before or after template removal was modified with NH₂- or COOH-groups and then grafted with PEG chains. The anticancer drug tamoxifen was loaded into the organic groups’ modified and PEGylated nanoparticles by an incipient wetness impregnation procedure. The amount of loaded drug and the release properties depend on whether modification of the nanoparticles was performed before or after the template removal step. The parent and drug-loaded samples were characterized by XRD, N₂ physisorption, thermal gravimetric analysis, and ATR FT-IR spectroscopy. ATR FT-IR spectroscopic data and density functional theory (DFT) calculations supported the interaction between the mesoporous silica surface and tamoxifen molecules and pointed out that the drug molecule interacts more strongly with the silicate surface terminated by silanol groups than with the surface modified with carboxyl groups. A sustained tamoxifen release profile was obtained by an in vitro experiment at pH = 7.0 for the PEGylated formulation modified by COOH groups after the template removal. Free drug and formulated tamoxifen samples were further investigated for antiproliferative activity against MCF-7 cells. Full article

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15 pages, 3003 KiB

Open AccessArticle

Characterization of Modified Natural Minerals and Rocks for Possible Adsorption and Catalytic Use

by Kateřina Strejcová, Zdeněk Tišler, Eliška Svobodová and Romana Velvarská

Molecules 2020, 25(21), 4989; https://doi.org/10.3390/molecules25214989 - 28 Oct 2020

Cited by 10 | Viewed by 1994

Abstract

This study focused on natural materials such as clinoptilolite (CLI), metakaolin (MK), marlstone (MRL) and phonolite (PH). Clinoptilolite is one of the most known and common natural minerals (zeolites) with a unique porous structure, metakaolin is calcined kaolin clay, marlstone is a sedimentary [...] Read more.

This study focused on natural materials such as clinoptilolite (CLI), metakaolin (MK), marlstone (MRL) and phonolite (PH). Clinoptilolite is one of the most known and common natural minerals (zeolites) with a unique porous structure, metakaolin is calcined kaolin clay, marlstone is a sedimentary rock and phonolite is an igneous rock composed of alkali feldspar and other minerals. These natural materials are mainly used in the building industry (additions for concrete mixtures, production of paving, gravels) or for water purification, but the modification of their chemical, textural and mechanical properties makes these materials potentially usable in other industries, especially in the chemical industry. The modification of these natural materials and rocks was carried out by leaching using 0.1 M HCl (D1 samples) and then using 3 M HCl (D2 samples). This treatment could be an effective tool to modify the structure and composition of these materials. Properties of modified materials were determined by N₂ physisorption, Hg porosimetry, temperature programmed desorption of ammonia (NH₃-TPD), X-ray fluorescence (XRF), X-ray powder diffraction (XRD), diffuse reflectance infrared Fourier transform (DRIFT) and CO₂ adsorption using thermogravimetric analysis (TGA). The results of N₂ physisorption measurements showed that that the largest increase of specific surface area was for clinoptilolite leached using 3M HCl. There was also a significant increase of the micropore volume in the D2 samples. The only exception was marlstone, where the volume of micropores was zero even in the leached sample. Clinoptilolite had the highest acidity and sorption capacity of CO₂. TGA showed that the amount of CO₂ adsorbed was not significantly related to the increase in specific surface area and the opening of micropores. Hg porosimetry showed that acid leaching using 0.1 M HCl and 3 M HCl resulted in a significant increase in the macropore volume in phonolite, and during leaching using 3M HCl there was an increase of the mesopore volume. From the better properties, cost-efficient and environmental points of view, the use of these materials could be an interesting solution for catalytic and sorption applications. Full article

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17 pages, 2446 KiB

Open AccessArticle

Tris(2-Aminoethyl)Amine/Metal Oxides Hybrid Materials—Preparation, Characterization and Catalytic Application

by Katarzyna Stawicka and Maria Ziolek

Molecules 2020, 25(20), 4689; https://doi.org/10.3390/molecules25204689 - 14 Oct 2020

Cited by 1 | Viewed by 2680

Abstract

Three different metal oxides (basic MgO, basic-acidic Al₂O₃ and acidic-basic Nb₂O₅) characterized by comparable surface areas (MgO—130 m²/g; Al₂O₃—172 m²/g and Nb₂O₅—123 m² [...] Read more.

Three different metal oxides (basic MgO, basic-acidic Al₂O₃ and acidic-basic Nb₂O₅) characterized by comparable surface areas (MgO—130 m²/g; Al₂O₃—172 m²/g and Nb₂O₅—123 m²/g) and pore systems (domination of mesopores with narrow pore size distribution) were modified with tris(2-aminoethyl)amine (TAEA) via two methods: (i) direct anchoring of amine on metal oxide and (ii) anchoring of amine on metal oxide functionalized with (3-chloropropyl)trimethoxysilane. The obtained hybrid materials were characterized in terms of effectiveness of modifier anchoring (elemental analysis), their structural/textural properties (nitrogen adsorption/desorption, XRD), acidity/basicity of support (2-propanol dehydration and dehydrogenation, dehydration and cyclization of 2,5-hexanedione), states of modifier deposited on supports (XPS, FTIR, UV–VIS) and the strength of interaction between the modifier and the support (TG/DTG). It was evidenced that acidic-basic properties of metal oxides as well as the procedure of modification with TAEA determined the ways of amine anchoring and the strength of its interaction with the support. The obtained hybrid materials were tested in Knoevenagel condensation between furfural and malononitrile. The catalysts based on MgO showed superior activity in this reaction. It was correlated with the way of TAEA anchoring on basic MgO and the strength of modifier anchoring on the support. To the best of our knowledge tris(2-aminoethyl)amine has not been used as a modifier of solid supports for enhancement of the catalyst activity in Knoevenagel condensation. Full article

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14 pages, 4600 KiB

Open AccessArticle

Synthesis of FAU-Type Zeolite Membranes with Antimicrobial Activity

by T. Jean Daou, Thomas Dos Santos, Habiba Nouali, Ludovic Josien, Laure Michelin, Laurent Pieuchot and Patrick Dutournie

Molecules 2020, 25(15), 3414; https://doi.org/10.3390/molecules25153414 - 28 Jul 2020

Cited by 12 | Viewed by 3209

Abstract

In this study, a layer of a pure and dense phase of FAU-type zeolite was synthesized directly on the surface of α-Al₂O₃ plane macroporous support. Before hydrothermal synthesis, a step of cleaning of the support by an anionic detergent was [...] Read more.

In this study, a layer of a pure and dense phase of FAU-type zeolite was synthesized directly on the surface of α-Al₂O₃ plane macroporous support. Before hydrothermal synthesis, a step of cleaning of the support by an anionic detergent was performed, a roughness surface is created, allowing the anchoring of the zeolite nuclei and then their growth, favoring in this sense the formation of a homogeneous zeolite layer. The obtained membranes were fully characterized using X-ray diffraction analysis (XRD), nitrogen sorption, scanning electron microscopy (SEM), and mercury porosimetry. After 24 h of thermal treatment at 75 °C, a homogeneous zeolite layer composed of bipyramidal crystals of FAU-type zeolite is obtained with a thickness of about 2.5 µm. No obvious defects or cracks can be observed. It was found that the increase in heating temperature could lead to the appearance of an impurity phase, GIS-type zeolite. Then the ideal zeolite membrane was exchanged with Ag⁺ or Zn²⁺ cations to studies their antimicrobial properties. Zeolites membranes exchanged with Ag⁺ showed an agar-diffusive bactericidal activity against gram negative Escherichia coli (E. coli) bacteria. Zn²⁺ exchanged zeolite membrane presented a bacteriostatic activity that is less diffusive in agar. As expected, non-exchanged zeolite membrane (in its Na⁺ form) have no effect on bacterial activity. This process is particularly interesting for the synthesis of a good quality FAU-type zeolite membranes with antimicrobial properties. Full article

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14 pages, 18475 KiB

Open AccessArticle

Preparation of Poly(glycidyl methacrylate) (PGMA) and Amine Modified PGMA Adsorbents for Purification of Glucosinolates from Cruciferous Plants

by Li Cheng, Jianpeng Wu, Hao Liang and Qipeng Yuan

Molecules 2020, 25(14), 3286; https://doi.org/10.3390/molecules25143286 - 20 Jul 2020

Cited by 6 | Viewed by 3787

Abstract

Glucosinolates (GLs) are of great interest for their potential as antioxidant and anticancer compounds. In this study, macroporous crosslinked copolymer adsorbents of poly (glycidyl methacrylate) (PGMA) and its amine (ethylenediamine, diethylamine, triethylamine)-modified derivatives were prepared and used to purify the GLS glucoerucin in [...] Read more.

Glucosinolates (GLs) are of great interest for their potential as antioxidant and anticancer compounds. In this study, macroporous crosslinked copolymer adsorbents of poly (glycidyl methacrylate) (PGMA) and its amine (ethylenediamine, diethylamine, triethylamine)-modified derivatives were prepared and used to purify the GLS glucoerucin in a crude extract obtained from a cruciferous plant. These four adsorbents were evaluated by comparing their adsorption/desorption and decolorization performance for the purification of glucoerucin from crude plant extracts. According to the results, the strongly basic triethylamine modified PGMA (PGMA-III) adsorbent showed the best adsorption and desorption capacity of glucoerucin, and its adsorption data was a good fit to the Freundlich isotherm model and pseudo-second-order kinetics; the PGMA adsorbent gave the optimum decolorization performance. Furthermore, dynamic adsorption/desorption experiments were carried out to optimize the purification process. Two glass columns were serially connected and respectively wet-packed with PGMA and PGMA-III adsorbents so that glucoerucin could be decolorized and isolated from crude extracts in one process. Compared with KCl solution, aqueous ammonia was a preferable desorption solvent for the purification of glucoerucin and overcame the challenges of desalination efficiency, residual methanol and high operation costs. The results showed that after desorption with 10% aqueous ammonia, the purity of isolated glucoerucin was 74.39% with a recovery of 80.63%; after decolorization with PGMA adsorbent, the appearance of glucoerucin was improved and the purity increased by 11.30%. The process of using serially connected glass columns, wet-packed with PGMA and PGMA-III, may provide a simple, low-cost, and efficient method for the purification of GLs from cruciferous plants. Full article

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16 pages, 3113 KiB

Open AccessArticle

New Microporous Lanthanide Organic Frameworks. Synthesis, Structure, Luminescence, Sorption, and Catalytic Acylation of 2-Naphthol

by Dana Bejan, Lucian Gabriel Bahrin, Sergiu Shova, Narcisa Laura Marangoci, Ülkü Kökҫam-Demir, Vasile Lozan and Christoph Janiak

Molecules 2020, 25(13), 3055; https://doi.org/10.3390/molecules25133055 - 03 Jul 2020

Cited by 13 | Viewed by 2986

Abstract

New metal-organic frameworks (MOF) with lanthanum(III), cerium(III), neodymium(III), europium(III), gadolinium(III), dysprosium(III), and holmium(III)] and the ligand precursor 1,3,5-tris(4-carboxyphenyl)-2,4,6-trimethylbenzene (H₃L) were synthesized under solvothermal conditions. Single crystal x-ray analysis confirmed the formation of three-dimensional frameworks of [LnL(H [...] Read more.

New metal-organic frameworks (MOF) with lanthanum(III), cerium(III), neodymium(III), europium(III), gadolinium(III), dysprosium(III), and holmium(III)] and the ligand precursor 1,3,5-tris(4-carboxyphenyl)-2,4,6-trimethylbenzene (H₃L) were synthesized under solvothermal conditions. Single crystal x-ray analysis confirmed the formation of three-dimensional frameworks of [LnL(H₂O)₂]_n·xDMF·yH₂O for Ln = La, Ce, and Nd. From the nitrogen sorption experiments, the compounds showed permanent porosity with Brunauer-Emmett-Teller (BET) surface areas of about 400 m²/g, and thermal stability up to 500 °C. Further investigations showed that these Ln-MOFs exhibit catalytic activity, paving the way for potential applications within the field of catalysis. Full article

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12 pages, 4247 KiB

Open AccessArticle

Preparation of Microspheres and Monolithic Microporous Carbons from the Pyrolysis of Template-Free Hyper-Crosslinked Oligosaccharides Polymer

by Anastasia Anceschi, Andrea Binello, Fabrizio Caldera, Francesco Trotta and Marco Zanetti

Molecules 2020, 25(13), 3034; https://doi.org/10.3390/molecules25133034 - 02 Jul 2020

Cited by 4 | Viewed by 2220

Abstract

Carbon-based materials with different morphologies have special properties suitable for application in adsorption, catalysis, energy storage, and so on. Carbon spheres and carbon monoliths are also nanostructured materials showing promising results. However, the preparation of these materials often require the use of a [...] Read more.

Carbon-based materials with different morphologies have special properties suitable for application in adsorption, catalysis, energy storage, and so on. Carbon spheres and carbon monoliths are also nanostructured materials showing promising results. However, the preparation of these materials often require the use of a template, which aggravates their costs, making the operations for their removal complex. In this work, hollow carbon microspheres and carbon monolith were successfully prepared via carbonization of hyper-crosslinked polymer based on either cyclodextrins or amylose, in a template-free way. The carbons obtained are of the microporous type, showing a surface area up to 610 m²/g, and a narrow pore distribution, typically between 5 and 15 Å. Full article

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