Special Issue "Covalent Organic Frameworks"

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Organic Crystalline Materials".

Deadline for manuscript submissions: closed (28 June 2023) | Viewed by 3157

Special Issue Editors

Dr. Xing Han
E-Mail Website
Guest Editor
Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
Interests: covalent organic frameworks
Dr. Tianqiong Ma
E-Mail Website
Guest Editor
Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720, USA
Interests: covalent organic frameworks

Special Issue Information

Dear Colleagues,

Covalent organic frameworks (COFs) are a new class of crystalline porous organic material possessing two- or three- dimensional structures. COFs are constructed from pre-designed organic building units connecting by strong covalent bonds between light atoms (e.g., B, C, N, O, P, Si). Since they were firstly reported by Yaghi et al. in 2005, COFs have emerged as a material with a wealth of applications, such as sorption, separation, optoelectronics, catalysis, sensors, drug delivery, energy storage, etc. COFs exemplify the manner in which reticular chemistry is practiced, with the control at molecular level being exercised over matter. The facile bottom-up synthesis of COFs introducing precise perturbations in chemical composition results in the highly controlled tunability of structural diversity and framework properties such as porosity, conjugation property, etc.

As a crystalline material, progress in developing their chemistry often dominates the ability to crystallize them. In most cases, reversible reactions have been used to build COF materials so that self-correction can be realized in the crystal growth of COFs by chemical equilibrium. For example, borate ester condensation reaction and imine condensation reaction are mostly used in the crystal growth of COFs. However, the strength of covalent bonding between the building units often yields polycrystalline products. Hence, structural analysis of COFs usually combines multiple characterization methods, for example, powder X-ray diffraction (PXRD) modeling and TEM techniques. In 2018, large-sized single-crystal COFs were obtained, enabling the use of single-crystal X-ray diffraction to identify atomically precise COF structures.

In this Special Issue, we will focus on the design, synthesis, crystal growth, properties, and emerging applications of COFs.

Dr. Xing Han
Dr. Tianqiong Ma
Guest Editors

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Keywords

  • covalent organic frameworks
  • single crystal
  • reticular chemistry
  • framework material
  • porous organic material

Published Papers (2 papers)

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Research

Article
Three-Component Covalent Organic Framework Nanosheets for the Detection of MicroRNAs
Crystals 2022, 12(11), 1628; https://doi.org/10.3390/cryst12111628 - 13 Nov 2022
Cited by 1 | Viewed by 999
Abstract
The development of new techniques for the detection of microRNAs (miRNAs) is highly desirable. Herein, a new crystalline three-component covalent organic framework (COF) termed EB-TAPB-TFP COF was synthesized under solvothermal conditions utilizing 1,3,5-triformylphloroglucinol, 1,3,5-tris(4-aminophenyl)benzene and ethidium bromide as monomers. Interestingly, EB-TAPB-TFP COF can [...] Read more.
The development of new techniques for the detection of microRNAs (miRNAs) is highly desirable. Herein, a new crystalline three-component covalent organic framework (COF) termed EB-TAPB-TFP COF was synthesized under solvothermal conditions utilizing 1,3,5-triformylphloroglucinol, 1,3,5-tris(4-aminophenyl)benzene and ethidium bromide as monomers. Interestingly, EB-TAPB-TFP COF can be self-exfoliated into two-dimensional nanosheets (NSs) in an aqueous medium. The obtained EB-TAPB-TFP NSs exhibited a remarkable fluorescence intensity enhancement in the presence of a DNA-miRNA heteroduplex when compared to the presence of single-stranded DNA and other phosphate-based small molecules, making it promising in the detection of miRNA without tagging any fluorescent marker. Moreover, the EB-TAPB-TFP NSs can also be used as sensing material for the detection of a DNA-miRNA heteroduplex using the quartz crystal microbalance technique, which is in good agreement with the fluorescence sensing result. The exploration of COF-based sensors in this work demonstrates a new pathway for the selective detection of miRNAs. Full article
(This article belongs to the Special Issue Covalent Organic Frameworks)
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Article
2D Microporous Covalent Organic Frameworks as Cobalt Nanoparticle Supports for Electrocatalytic Hydrogen Evolution Reaction
Crystals 2022, 12(7), 880; https://doi.org/10.3390/cryst12070880 - 21 Jun 2022
Cited by 2 | Viewed by 1528
Abstract
Covalent organic frameworks (COFs) are a new class of porous crystalline polymers, which are considered to be excellent supports for metal nanoparticles (MNPs) due to their highly ordered structure, chemical tunability, and porosity. In this work, two novel ultra-microporous COFs, JUC−624 and JUC−625, [...] Read more.
Covalent organic frameworks (COFs) are a new class of porous crystalline polymers, which are considered to be excellent supports for metal nanoparticles (MNPs) due to their highly ordered structure, chemical tunability, and porosity. In this work, two novel ultra-microporous COFs, JUC−624 and JUC−625, with narrow pore size distribution have been synthesized and used for the confined growth of ultrafine Co nanoparticles (CoNPs) with high loading. In an alkaline environment, the produced materials were investigated as electrocatalysts for the hydrogen evolution reaction (HER). Electrochemical test results show that CoNPs@COFs have a Tafel slope of 84 mV·dec−1, an onset overpotential of 105 mV, and ideal stability. Remarkably, CoNPs@JUC−625 required only 146 mV of overpotential to afford a current density of 10 mA cm−2. This research will open up new avenues for making COF-supported ultrafine MNPs with good dispersity and stability for extensive applications. Full article
(This article belongs to the Special Issue Covalent Organic Frameworks)
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