Design Of Covalent Organic Frameworks Research Articles

Structural Modulation of Covalent Organic Frameworks for Efficient Hydrogen Peroxide Electrocatalysis.

The electrochemical production of hydrogen peroxide (H2O2) using metal-free catalysts has emerged as a viable and sustainable alternative to the conventional anthraquinone process. However, the precise architectural design of these electrocatalysts poses a significant challenge, requiring intricate structural engineering to optimize electron transfer during the oxygen reduction reaction (ORR). Herein, we introduce a novel design of covalent organic frameworks (COFs) that effectively shift the ORR from a four-electron to a more advantageous two-electron pathway. Notably, the JUC-660 COF, with strategically charge-modified benzyl moieties, achieved a continuous high H2O2 yield of over 1200 mmol g-1 h-1 for an impressive duration of over 85 hours in a flow cell setting, marking it as one of the most efficient metal-free and non-pyrolyzed H2O2 electrocatalysts reported to date. Theoretical computations alongside in situ infrared spectroscopy indicate that JUC-660 markedly diminishes the adsorption of the OOH* intermediate, thereby steering the ORR towards the desired pathway. Furthermore, the versatility of JUC-660 was demonstrated through its application in the electro-Fenton reaction, where it efficiently and rapidly removed aqueous contaminants. This work delineates a pioneering approach to altering the ORR pathway, ultimately paving the way for the development of highly effective metal-free H2O2 electrocatalysts.

Structural Modulation of Covalent Organic Frameworks for Efficient Hydrogen Peroxide Electrocatalysis

AbstractThe electrochemical production of hydrogen peroxide (H2O2) using metal‐free catalysts has emerged as a viable and sustainable alternative to the conventional anthraquinone process. However, the precise architectural design of these electrocatalysts poses a significant challenge, requiring intricate structural engineering to optimize electron transfer during the oxygen reduction reaction (ORR). Herein, we introduce a novel design of covalent organic frameworks (COFs) that effectively shift the ORR from a four‐electron to a more advantageous two‐electron pathway. Notably, the JUC‐660 COF, with strategically charge‐modified benzyl moieties, achieved a continuous high H2O2 yield of over 1200 mmol g−1 h−1 for an impressive duration of over 85 hours in a flow cell setting, marking it as one of the most efficient metal‐free and non‐pyrolyzed H2O2 electrocatalysts reported to date. Theoretical computations alongside in situ infrared spectroscopy indicate that JUC‐660 markedly diminishes the adsorption of the OOH* intermediate, thereby steering the ORR towards the desired pathway. Furthermore, the versatility of JUC‐660 was demonstrated through its application in the electro‐Fenton reaction, where it efficiently and rapidly removed aqueous contaminants. This work delineates a pioneering approach to altering the ORR pathway, ultimately paving the way for the development of highly effective metal‐free H2O2 electrocatalysts.

Computer-Aided Design of Covalent Organic Frameworks for SF6 Capture: The Combination of High-Throughput Screening and Machine Learning

Computer-Aided Design of Covalent Organic Frameworks for SF₆ Capture: The Combination of High-Throughput Screening and Machine Learning

Rational Design of Covalent Organic Frameworks as Photocatalysts for Water Splitting

AbstractPhotocatalytic water splitting for hydrogen production represents a crucial approach for obtaining green energy through artificial solar energy utilization, offering a sustainable method for energy generation that helps mitigate energy shortages and protect the environment. Among the numerous photocatalytic materials, covalent organic frameworks (COFs) have garnered significant attention and intensive study from researchers due to their distinctive benefits, such as porosity, pre‐design capability, and tunability at the atomic level. Significant advancements are made in the development of materials, enhancement of performance, and comprehension of mechanisms. In this review, recent advancements in COF‐based photocatalytic water splitting are spotlighted, both in half‐reactions and overall reactions, with a particular emphasis on the rational design of COF structures to regulate the materials' optical and electrical properties, as well as the fundamental processes of photocatalysis. Drawing from current research in this field, the existing challenges, and potential opportunities are also discussed for future development.

Rational Design of Covalent Organic Frameworks with Redox-Active Catechol Moieties for High-Performance Overall Photosynthesis of Hydrogen Peroxide

Rational Design of Covalent Organic Frameworks with Redox-Active Catechol Moieties for High-Performance Overall Photosynthesis of Hydrogen Peroxide

Robust Thiazole-Linked Covalent Organic Frameworks for Water Sensing with High Selectivity and Sensitivity.

The rational design of covalent organic frameworks (COFs) with hydrochromic properties is of significant value because of the facile and rapid detection of water in diverse fields. In this report, we present a thiazole-linked COF (TZ-COF-6) sensor with a large surface area, ultrahigh stability, and excellent crystallinity. The sensor was synthesized through a simple three-component reaction involving amine, aldehyde, and sulfur. The thiazole and methoxy groups confer strong basicity to TZ-COF-6 at the nitrogen sites, making them easily protonated reversibly by water. Therefore, TZ-COF-6 displayed color change visible to the naked eye from yellow to red when protonated, along with a red shift in absorption in the ultraviolet-visible diffuse reflectance spectra (UV-vis DRS) when exposed to water. Importantly, the water-sensing process was not affected by polar organic solvents, demonstrating greater selectivity and sensitivity compared to other COF sensors. Therefore, TZ-COF-6 was used to detect trace amounts of water in organic solvents. In strong polar solvents, such as N,N-dimethyl formamide (DMF) and ethanol (EtOH), the limit of detection (LOD) for water was as low as 0.06% and 0.53%, respectively. Even after 8 months of storage and 15 cycles, TZ-COF-6 retained its original crystallinity and detection efficiency, displaying high stability and excellent cycle performance.

Research progress of the combination of COFs materials with food safety detection.

Covalent organic frameworks (COFs) have received lots of attention due to their multiple advantages such as high specific surface area, controlled pore size, and excellent stability. When detecting food contaminants, the matrix effect brought by complex food samples can significantly affect the accuracy of the results. How to attenuate matrix effect has always been a major challenge. Utilizing the advantages of COFs and applying them to detect food contaminants is currently a key research direction. The aim of this work is to provide a systematic summary of sample pretreatment techniques and detection techniques combined with COFs, which include almost all current techniques combined with COFs. In addition, the principles of combining COFs with different techniques are explained. Finally, the research foci and development direction of COFs in food contaminant detection are discussed. This is an important reference for the future development of food safety and the design of COFs.

Cooperative Synthesis of Raspberry-Like Covalent Organic Framework-Polymer Particles with a Radial Single-Crystal Grain Orientation.

Despite many efforts devoted toward the design of covalent organic frameworks (COFs) at the framework level by selecting the building blocks, their organization in the nano to meso regimes is often neglected. Moreover, the importance of processability for their applications has recently emerged and the synthesis of COF nanostructures without agglomeration is still a challenge. Herein, the first example of hybrid COF-polymer particles for which polymers are used to manipulate the 2D COF growth along a specific direction is reported. The study examines how the nature, chain-end functionality, and molar mass of the polymer influence the shaping of hybrid 2D boronate ester-linked COF-polymer particles. Catechol-poly(N-butyl acrylate) leads to the self-assembly of crystallites into quasi-spherical structures while catechol-poly(N-isopropylacrylamide) mediates the synthesis of raspberry-like COF-polymer particles with radial grain orientation. Scanning and transmission electron microscopies (SEM and TEM) and 4D-STEM-ACOM (automated crystal orientation mapping) highlight the single-crystal character of these domains with one plane family throughout the particles. Interestingly, the presence of PNIPAm on the particle surface allows their drying without co-crystallization and enables their resuspension. Kinetic investigations show that catechol-PnBuA acts as a modulator and catechol-PNIPAm induces a template effect, introducing supramolecular self-assembly properties into particles to create new morphologies with higher structural complexity, beyond the framework level.

A Data-Driven Search of Two-Dimensional Covalent Organic Frameworks for Visible-Light-Driven Overall Water Splitting.

Two-dimensional (2D) covalent organic frameworks (COFs) with versatile structural and optoelectronic properties that can be tuned with building blocks and topological structures have received widespread attention for photocatalytic water splitting in recent years. However, few of these have been reported for overall water splitting under visible light. Here, we present a data-driven search of 2D COFs capable of visible-light-driven overall water splitting by combining high-throughput first-principles computations and experimental validations. Seven 2D COFs were identified to be capable of overall water splitting from the CoRE COF database, and their photocatalytic activities were further verified and optimized by our preliminary experiments. The production rates of H2 and O2 reached 80 and 32 μmol g-1 h-1, respectively, without using sacrificial agents. This work represents an attempt to explore 2D COFs for visible-light-driven overall water splitting with a data-driven approach that could accelerate the discovery and design of COFs toward photocatalytic overall water splitting.

Catalyst: The roles of chemistry in clean water for all

Dr. Young-Shin Jun is a professor in the Department of Energy, Environmental & Chemical Engineering and director of the Environmental NanoChemistry Laboratory at Washington University in St. Louis. She solves important energy and environmental challenges by using nanoscale interfacial reactions and nucleation. Her research interests in clean water include the development of novel materials, membrane processes, resource recovery, and managed aquifer recharge. She received a 2011 US National Science Foundation CAREER award, and she was named a 2015 Kavli Fellow by the US National Academy of Sciences, a 2016 Frontier of Engineering Fellow by the US National Academy of Engineering, and a 2019 American Chemical Society Fellow. Dr. Young-Shin Jun is a professor in the Department of Energy, Environmental & Chemical Engineering and director of the Environmental NanoChemistry Laboratory at Washington University in St. Louis. She solves important energy and environmental challenges by using nanoscale interfacial reactions and nucleation. Her research interests in clean water include the development of novel materials, membrane processes, resource recovery, and managed aquifer recharge. She received a 2011 US National Science Foundation CAREER award, and she was named a 2015 Kavli Fellow by the US National Academy of Sciences, a 2016 Frontier of Engineering Fellow by the US National Academy of Engineering, and a 2019 American Chemical Society Fellow. Reaction: Harnessing reactive oxygen species (ROS) for water purificationZhu et al.ChemJune 08, 2023In BriefReactive oxygen species (ROS) play a vital role in water purification. We outline their natural presence in the water matrix through a variety of chemical and photochemical processes and discuss advanced oxidation processes (AOPs) that draw inspiration from natural principles to boost ROS generation. Moreover, we summarize key challenges in ROS-based technologies for water and wastewater treatment, explain their fundamental origins, and propose strategies for minimizing energy and chemical usage while mitigating the formation of toxic byproducts. Full-Text PDF Reaction: Avoid fairy dust when engineering water-purification technologiesPaul WesterhoffChemJune 08, 2023In BriefThis Catalysis article discusses the risks of using nanomaterials for water purification and alternative strategies, painting a fuller picture of research in clean water. Full-Text PDF Molecular design of covalent organic frameworks for seawater desalination: A state-of-the-art reviewJrad et al.ChemMay 11, 2023In BriefConventional materials’ limitations are slowing the innovation in desalination to make it more accessible and energy efficient. Novel materials, such as covalent organic frameworks (COFs), provide design flexibility and could help achieve a breakthrough in desalination. This requires a comprehensive knowledge of desalination technologies and their technical challenges, as well as an understanding of the design principles of COFs. This report comprehensively discusses both of these issues while providing insights on how to design COFs for each specific desalination technology. Full-Text PDF

Recent Advances in the Use of Covalent Organic Frameworks as Heterogenous Photocatalysts in Organic Synthesis.

Organic photochemistryisintensely developed in the 1980s, in which the nature of excited electronic states and the energy and electron transfer processes arethoroughly studied and finally well-understood. This knowledge from molecular organic photochemistry can be transferred to the design of covalent organic frameworks (COFs) as active visible-light photocatalysts. COFs constitute a new class of crystalline porous materials with substantial application potentials. Featured with outstanding structural tunability, large porosity, high surface area, excellent stability, and unique photoelectronic properties, COFs are studied as potential candidates in various research areas (e.g., photocatalysis). This review aims to provide the state-of-the-art insights into the design of COF photocatalysts (pristine, functionalized, and hybrid COFs) for organic transformations. The catalytic reaction mechanism of COF-based photocatalysts and the influence of dimensionality and crystallinity on heterogenous photocatalysis performance are also discussed, followed by perspectives and prospects on the main challenges and opportunities in future research of COFs and COF-based photocatalysts.

Role of Intralayer Hydrogen Bonding in the Fast Crystallization of the Hydrazone-Linked Nanoporous Covalent Organic Framework for Catalytic Suzuki–Miyaura Cross-Coupling Reactions

Covalent organic frameworks (COFs) are the emerging smart materials that can be designed and synthesized by tuning their structural diversity and topology for various applications. Despite vast advancements in the design of COFs, the synthetic methodologies to construct COFs are always a significant challenge. Herein, we demonstrate a fast crystallization in hydrazone-based Bth-Tp-COF, synthesized via a Schiff-base reaction between benzene-1,3,5-tricarbohydrazide (Bth) and triformylphloroglucinol (Tp) linkers under stirred conditions. The growth of the COF was typically completed in 30 min and likely driven by intra- and interlayer hydrogen bonding in COF layers, leading to the fast crystallization. Here, the intralayer hydrogen bonding prevented in-plane bond rotation, while the interlayer hydrogen bonding provided rigidity to the COF layers favoring the antiparallel stacking model. The synthesized Bth-Tp-COF was found to be highly stable in harsh chemicals such as 12 M HCl, 12 M NaOH, TFA, and water for 5 days. Moreover, when we doped palladium (Pd) in Bth-Tp-COF, the resulting Pd/Bth-Tp-COF was found to be a highly efficient heterogeneous catalyst for the Suzuki–Miyaura cross-coupling reaction that completed in a quick reaction time of only 20 min with excellent yields. In addition, Pd/Bth-Tp-COF displayed high activity in the recycling experiment with a slight decrease in its crystallinity up to five catalytic cycles. The fast crystallization and metal doping strategy in COFs open up several opportunities to develop excellent heterogeneous catalysts for various chemical transformations.

Rational Design of Covalent Organic Frameworks as Gas Diffusion Layers for Multi-atmosphere Lithium-Air Batteries.

Non-aqueous Li-air batteries, despite their high energy density and low cost, have not been deployed practically due to their instability in ambient air, where moisture causes parasitic reactions and shortens their life drastically. Here, we demonstrate the rational design of nanoporous covalent organic frameworks (COFs) as effective gas diffusion layers (GDLs) to address this constraint. The COF GDLs, with a tailor-made pore size of ~1.4 nm and superhydrophobicity can limit the intrusion of organic electrolytes and moisture into the gas diffusion channels, enabling high capacity, fast kinetics, and excellent stability of the Li-air batteries. Moreover, we achieve multi-atmosphere Li-air batteries, which can stably cycle under open ambient air (relative humidity up to 95%) and even in various atmospheres with looping oxygen, humid air, and carbon dioxide. The design principles of our COF GDLs can be universally applied in energy storage and electrochemical systems using organic electrolytes.

Rational Design of Covalent Organic Frameworks as Gas Diffusion Layers for Multi‐atmosphere Lithium‐Air Batteries

AbstractNon‐aqueous Li‐air batteries, despite their high energy density and low cost, have not been deployed practically due to their instability in ambient air, where moisture causes parasitic reactions and shortens their life drastically. Here, we demonstrate the rational design of nanoporous covalent organic frameworks (COFs) as effective gas diffusion layers (GDLs) to address this constraint. The COF GDLs, with a tailor‐made pore size of ≈1.4 nm and superhydrophobicity, can limit the intrusion of organic electrolytes and moisture into the gas diffusion channels, enabling high capacity, fast kinetics, and excellent stability of the Li‐air batteries. Moreover, we achieve multi‐atmosphere Li‐air batteries, which can stably cycle under open ambient air (relative humidity up to 95 %) and even in various atmospheres with looping oxygen, humid air, and carbon dioxide. The design principles of our COF GDLs can be universally applied in energy storage and electrochemical systems using organic electrolytes.

Integrated interfacial design of covalent organic framework photocatalysts to promote hydrogen evolution from water

Attempts to develop photocatalysts for hydrogen production from water usually result in low efficiency. Here we report the finding of photocatalysts by integrated interfacial design of stable covalent organic frameworks. We predesigned and constructed different molecular interfaces by fabricating ordered or amorphous π skeletons, installing ligating or non-ligating walls and engineering hydrophobic or hydrophilic pores. This systematic interfacial control over electron transfer, active site immobilisation and water transport enables to identify their distinct roles in the photocatalytic process. The frameworks, combined ordered π skeletons, ligating walls and hydrophilic channels, work under 300–1000 nm with non-noble metal co-catalyst and achieve a hydrogen evolution rate over 11 mmol g–1 h–1, a quantum yield of 3.6% at 600 nm and a three-order-of-magnitude-increased turnover frequency of 18.8 h–1 compared to those obtained with hydrophobic networks. This integrated interfacial design approach is a step towards designing solar-to-chemical energy conversion systems.

Rational design of covalent organic frameworks with high capacity and stability as a lithium-ion battery cathode.

A two-dimensional covalent organic framework (NTCDI-COF) with rich redox active sites, high stability and crystallinity was designed and prepared. As a cathode material for lithium-ion batteries (LIBs), NTCDI-COF exhibits excellent electrochemical performance with an outstanding discharge capacity of 210 mA h g-1 at 0.1 A g-1 and high capacity retention of 125 mA h g-1 after 1500 cycles at 2 A g-1. A two-step Li+ insertion/extraction mechanism is proposed based on the ex situ characterization and density functional theory calculation. The constructed NTCDI-COF//graphite full cells can realize a good electrochemical performance.

Strategic design of covalent organic frameworks (COFs) for photocatalytic hydrogen generation

Covalent organic frameworks provide a platform for the integration of functional organic linkers into ordered yet tunable two-dimensional frameworks to yield π–π stacked conjugated materials for photocatalytic water splitting for hydrogen generation.

Multi-Scale Computer-Aided Design of Covalent Organic Frameworks for CO2 Capture in Wet Flue Gas

Discovery of remarkable porous materials for CO2 capture from wet flue gas is of great significance to reduce the CO2 emissions, but elucidating the most critical structure features for boosting CO2 capture capabilities remains a great challenge. Here, machine-learning-assisted Monte Carlo computational screening on 516 experimental covalent organic frameworks (COFs) identifies the superior secondary building units (SBUs) for wet flue gas separation using COFs, which are tetraphenylporphyrin units for boosting CO2 adsorption uptake and functional groups for boosting CO2/N2 selectivity. Accordingly, 1233 COFs are assembled using the identified superior SBUs. Density functional theory calculation analysis on frontier orbitals, electrostatic potential, and binding energy reveals the influencing mechanism of the SBUs on the wet flue gas separation performance. The "electron-donating-induced vdW interaction" effect is discovered to construct the better-performing COFs, which can achieve high CO2 uptake of 4.4 mmol·g-1 with CO2/N2 selectivity of 104.8. Meanwhile, the "electron-withdrawing-induced vdW + electrostatic coupling interaction" effect is unearthed to construct the better-performing COFs with superior CO2/N2 selectivity, which can reach 277.6 with CO2 uptake of 2.2 mmol·g-1; in this case, H2O plays a positive contribution in improving CO2/N2 selectivity. This work provides useful guidelines for designing optimized two-dimensional-COF adsorbents for wet flue gas separation.

Effective remediation of Pb2+ polluted environment by adsorption onto recyclable hydroxyl bearing covalent organic framework.

The removal of heavy metal ions from wastewater has attracted considerable interest because of their toxicity. Adsorption is one of the most promising methods for the removal of heavy metal ions due to its simplicity and effectiveness. Recently, covalent organic frameworks (COFs) have become promising adsorbents for effective wastewater remediation. However, many building blocks have been developed, and the design of COFs with high adsorption efficiency remains a challenge. Here, a covalent organic framework (DHTP-TPB COF) decorated with hydroxyl groups was developed for the efficient removal of Pb2+ ions. The DHTP-TPB COF showed excellent performance in adsorbing Pb2+ from aqueous solution. More importantly, DHTP-TPB COF exhibited high selectivity for Pb2+ compared to other competing ions, capturing Pb2+ ions with a removal efficiency of over 96% at pH 4. The results show that the DHTP-TPB COF exhibits excellent adsorption capacity at pH 4 of up to 154.3mg/g for Pb2+ ions; the value is comparable to many previously reported COFs. Moreover, the adsorbed Pb2+ ions could be easily eluted with a 0.1M EDTA solution, and the DHTP-TPB COF can be reused for more than five adsorption-desorption cycles without significant loss of adsorption capacity. Moreover, the adsorption mechanism was revealed using XPS analysis, indicating the formation of strong coordination-bonding interactions between hydroxyl and Pb2+ ions. Therefore, the DHTP-TPB COF prepared herein has high potential for the treatment of Pb2+-contaminated wastewater and is promising for the adsorption of Pb2+ ions in practical applications.

Bottom‐Up Interfacial Design of Covalent Organic Frameworks for Highly Efficient and Selective Electrocatalysis of CO2

Assembling molecular catalytic centers into crosslinked networks is widely used to fabricate heterogeneous catalysts but they often suffer loss in activity and selectivity accompanied by unclear causes. Here, a strategy for the construction of heterogeneous catalysts to induce activity and selectivity by bottom-up introduction of segregated electron-conduction and mass-transport interfaces into the catalytic materials is reported. The catalytic skeletons are designed to possess different π orderings for electron motion and the open channels are tailored to install finely engineered walls for mass transport, so that origins of activity and selectivity are correlated. The resultant covalent organic framework catalysts with ordered π skeletons and solvophobic pores increase activity by two orders of magnitude, enhance selectivity and energy efficiency by 70-fold, and broaden the voltage range, to promote CO2 transformation under ambient conditions. The results open a way to precise interfacial design of actionable heterogeneous catalysts for producing feedstocks from CO2 .