Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

Covalent organic frameworks (COFs) as an emerging class of crystalline porous materials have received much attention due to their tunable porosity, modifiable skeletons, and atomically precise structures. Besides, COFs can provide multiple high-rate charge carrier transport (electron, hole, and ion) pathways, including conjugated skeletons, overlapped π electron clouds among the stacked layers, and open channels with a variable chemical environment. Therefore, they have shown great potential in electrochemical energy storage (EES) and conversion (EEC). However, in bulk COFs, the defects always impede charge carrier conduction, and the difficulties in reaching deep-buried active sites by either electrons or ions lead to limited performance. To overcome these obstacles, numerous research studies have been carried out to obtain COF nanosheets (NSs). This review first describes the preparation strategies of COF NSs via bottom-up and top-down approaches. Then, the applications of bulk COFs and COF NSs in EES and EEC are summarized, such as in batteries, supercapacitors, and fuel cells. Finally, key challenges and future directions in these areas are discussed.

Bulk COFs and COF nanosheets for electrochemical energy storage and conversion

Summary Covalent organic frameworks (COFs) are a new type of crystalline porous polymers known for chemical stability, excellent structural regularity, robust framework, and inherent porosity, making them promising materials for capturing various types of pollutants from aqueous solutions. This review thoroughly presents the recent progress and advances of COFs and COF-based materials as superior adsorbents for the efficient removal of toxic heavy metal ions, radionuclides, and organic pollutants. Information about the interaction mechanisms between various pollutants and COF-based materials are summarized from the macroscopic and microscopic standpoints, including batch experiments, theoretical calculations, and advanced spectroscopy analysis. The adsorption properties of various COF-based materials are assessed and compared with other widely used adsorbents. Several commonly used strategies to enhance COF-based materials’ adsorption performance and the relationship between structural property and sorption ability are also discussed. Finally, a summary and perspective on the opportunities and challenges of COFs and COF-based materials are proposed to provide some inspiring information on designing and fabricating COFs and COF-based materials for environmental pollution management.

Orderly Porous Covalent Organic Frameworks-based Materials: Superior Adsorbents for Pollutants Removal from Aqueous Solutions

Covalent organic frameworks offer a molecular platform for integrating organic units into periodically ordered yet extended two- and three-dimensional polymers to create topologically well-defined polygonal lattices and built-in discrete micropores and/or mesopores. This polymer architecture is unique as it enables predesigning both primary- and high-order structures, greatly enhancing our capabilities of designing organic materials to produce predictable structures and to achieve unique properties and functions. Progress over the past 15 years in the design, synthesis and functional exploration of COFs has successively established the basis of the COF field and COFs have shown the great potential of chemistry in developing a class of amazing organic materials. In this review, we focus on analysing the historic developments of COFs to uncover a full materials and application picture by providing comprehensive yet clear guidance for molecular design, synthetic control and functional exploration. We scrutinise the structural components of COFs including building blocks, reactive sites and functional groups with the aim of finding the origins of structural designability and diversity, as well as multiple functionalities. We disclose strategies for designing and synthesising frameworks to construct various tailor-made interfaces, and for exploring skeletons and pores to design properties and functions. With well-defined skeletons, pores and interfaces that offer a chemical basis to trigger and control interactions with photons, excitons, phonons, polarons, electrons, holes, spins, ions and molecules, we illustrate the current status of our understandings of structure-property correlations, and unveil the principles for establishing a regime to design unique functions that originate from and are inherent to structures. We predict the key central issues in design and synthesis, the challenges in functional design and the future directions from the perspectives of chemistry, physics and materials science.

Covalent organic frameworks: an ideal platform for designing ordered materials and advanced applications

Uranium is a key element in the nuclear industry, but its unintended leakage has caused health and environmental concerns. Here we report a sp2 carbon-conjugated fluorescent covalent organic framework (COF) named TFPT-BTAN-AO with excellent chemical, thermal and radiation stability is synthesized by integrating triazine-based building blocks with amidoxime-substituted linkers. TFPT-BTAN-AO shows an exceptional UO22+ adsorption capacity of 427 mg g−1 attributable to the abundant selective uranium-binding groups on the highly accessible pore walls of open 1D channels. In addition, it has an ultra-fast response time (2 s) and an ultra-low detection limit of 6.7 nM UO22+ suitable for on-site and real-time monitoring of UO22+, allowing not only extraction but also monitoring the quality of the extracted water. This study demonstrates great potential of fluorescent COFs for radionuclide detection and extraction. By rational designing target ligands, this strategy can be extended to the detection and extraction of other contaminants. Porous materials for uranium capture have been developed in the past, but materials for simultaneous uranium capture and detection are scarce. Here the authors develop a stable covalent organic framework capable of adsorbing and detecting uranyl ions.

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Regenerable and stable sp 2 carbon-conjugated covalent organic frameworks for selective detection and extraction of uranium

Uranium is a key resource for the development of the nuclear industry, and extracting uranium from the natural seawater is one of the most promising ways to address the shortage of uranium resources Herein, a semiconducting covalent organic framework (named NDA-TN-AO) with excellent photocatalytic and photoelectric activities was synthesized The excellent photocatalytic effect endowed NDA-TN-AO with a high anti-biofouling activity by generating biotoxic reactive oxygen species and promoting photoelectrons to reduce the adsorbed UVI to insoluble UIV , thereby increasing the uranium extraction capacity Owing to the photoinduced effect, the adsorption capacity of NDA-TN-AO to uranium in seawater reaches 607 mg g-1 , which is 133 times of that in dark The NDA-TN-AO with enhanced adsorption capacity is a promising material for extracting uranium from the natural seawater

Regenerable Covalent Organic Frameworks for Photo-enhanced Uranium Adsorption from Seawater.

Stable sp2 carbon-conjugated covalent organic framework for detection and efficient adsorption of uranium from radioactive wastewater

Mercury is one of the most toxic elements in the environment. Recently, a number of covalent organic frameworks (COFs) were developed for simultaneous detection and removal of mercury. They rely on...

Regenerable Carbohydrazide-Linked Fluorescent Covalent Organic Frameworks for Ultrasensitive Detection and Removal of Mercury

Covalent organic frameworks (COFs) have shown extensive applications in energy storage, catalysis, and gas adsorption because of their regular pore structure, flexible topological connectivity, and...

Wei-Rong Cui

Papers

Regenerable and stable sp 2 carbon-conjugated covalent organic frameworks for selective detection and extraction of uranium

Regenerable Covalent Organic Frameworks for Photo-enhanced Uranium Adsorption from Seawater.

Stable sp2 carbon-conjugated covalent organic framework for detection and efficient adsorption of uranium from radioactive wastewater

Regenerable Carbohydrazide-Linked Fluorescent Covalent Organic Frameworks for Ultrasensitive Detection and Removal of Mercury

Covalent Organic Framework Nanosheet-Based Ultrasensitive and Selective Colorimetric Sensor for Trace Hg2+ Detection