Search

Covalent organic frameworks (COFs) with a donor‐acceptor (D−A) architecture have been investigated as prospective semiconducting materials, particularly for photocatalytic processes. The incorporation of electron donating and accepting moieties into the COF backbone creates nano heterojunctions, enhancing efficient light absorption, charge separation, and charge transport. Herein, three pyrene‐based COFs were well designed for the aerobic coupling of amines under air atmosphere with blue‐LED irradiation. Among the three COFs, the Py‐Por‐COF with D−A structure exhibits the highest photocatalytic performance and demonstrates a remarkable apparent quantum efficiency of 11.3 % at 420 nm. In addition, the Py‐Por‐COF maintains a good level of crystallinity and high yield even undergone four cycles, showcasing the exceptional potential of D−A structure COFs in the field of photocatalytic organic transformation. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) present significant and irreversible risks to both human health and the environment. Therefore, there is an urgent and important need for extensive research aimed at identifying suitable materials and effective technical approaches for VOC removal. Metal‐ and covalent organic frameworks (MOFs, COFs), along with covalent triazine frameworks (CTFs), represent an attractive class of porous materials characterized by adjustable structures, high porosity, and high specific surface areas. In recent years, these materials have rapidly advanced across various fields, including gas adsorption and separation, drug delivery, sensing, and heterogeneous catalysis. Notably, MOFs, COFs, and CTFs exhibit immense potential for the photocatalytic elimination of VOCs, since they behave as semiconductors with adjustable properties. This review offers an overview of the synthesis and structural relationships of MOFs, COFs, and CTFs while discussing the recent progress in photocatalytic VOC removal. Additionally, a comprehensive overview of the photocatalytic mechanism is presented. Finally, the current limitations and prospective future developments are discussed. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) emerge as innovative photocatalysts featuring systematically tuned chemical structures, nano-porosity, and photoelectric properties. We have shown in the last years that COFs are excellent photocatalysts and they are able to produce hydrogen peroxide (H2O2) from oxygen and water. Despite the recent surge in the photosynthesis of H2O2 using COFs, its subsequent application for tandem pollutant remediation as a tangible green alternative to Fenton chemistry has not yet been comprehensively explored. In this study, we synthesized three highly crystalline sp2 COFs with different donor–acceptor (D–A) strengths, employing triazine units as the electron acceptor moiety. The D–A alignment promotes photogenerated charge separation, augmenting the photocatalytic process, which resulted in the TMT-TT-COF achieving a H2O2 production rate of 1952 μmol g−1 h−1 without any sacrificial agents. The COFs also manifested a rapid photocatalytic degradation of bisphenol A (BPA) from a variety of real-life waterbodies. This study pioneers the in situ H2O2 production via COFs to subsequently generate other reactive oxygen species (ROS) for direct organic pollutant degradation in the visible region. [ABSTRACT FROM AUTHOR]

Electrochemical two‐electron water oxidation (2e WOR) is gaining surging research traction for sustainable hydrogen peroxide production. However, the strong oxidizing environment and thermodynamically competitive side‐reaction (4e WOR) posit as thresholds for the 2e WOR. We herein report a custom‐crafted covalent triazine network possessing strong oxidizing properties as a proof‐of‐concept metal‐free functional organic network electrocatalyst for catalyzing 2e WOR. As the first‐of‐its‐kind, the material shows a maximum of 89.9 % Faradaic Efficiency and 1428 μmol/h/cm2 H2O2 production rate at 3.0 V bias potential (vs reversible hydrogen electrode, RHE), which are either better or comparable to the state‐of‐the‐art electrocatalysts. We have experimentally confirmed a stepwise 2e WOR mechanism which was further computationally endorsed by density functional theory studies. [ABSTRACT FROM AUTHOR]

Electrochemical two‐electron water oxidation (2e WOR) is gaining surging research traction for sustainable hydrogen peroxide production. However, the strong oxidizing environment and thermodynamically competitive side‐reaction (4e WOR) posit as thresholds for the 2e WOR. We herein report a custom‐crafted covalent triazine network possessing strong oxidizing properties as a proof‐of‐concept metal‐free functional organic network electrocatalyst for catalyzing 2e WOR. As the first‐of‐its‐kind, the material shows a maximum of 89.9 % Faradaic Efficiency and 1428 μmol/h/cm2 H2O2 production rate at 3.0 V bias potential (vs reversible hydrogen electrode, RHE), which are either better or comparable to the state‐of‐the‐art electrocatalysts. We have experimentally confirmed a stepwise 2e WOR mechanism which was further computationally endorsed by density functional theory studies. [ABSTRACT FROM AUTHOR]

Electrochemical two‐electron water oxidation (2e WOR) is gaining surging research traction for sustainable hydrogen peroxide production. However, the strong oxidizing environment and thermodynamically competitive side‐reaction (4e WOR) posit as thresholds for the 2e WOR. We herein report a custom‐crafted covalent triazine network possessing strong oxidizing properties as a proof‐of‐concept metal‐free functional organic network electrocatalyst for catalyzing 2e WOR. As the first‐of‐its‐kind, the material shows a maximum of 89.9 % Faradaic Efficiency and 1428 μmol/h/cm2 H2O2 production rate at 3.0 V bias potential (vs reversible hydrogen electrode, RHE), which are either better or comparable to the state‐of‐the‐art electrocatalysts. We have experimentally confirmed a stepwise 2e WOR mechanism which was further computationally endorsed by density functional theory studies. [ABSTRACT FROM AUTHOR]

Electrochemical two‐electron water oxidation (2e WOR) is gaining surging research traction for sustainable hydrogen peroxide production. However, the strong oxidizing environment and thermodynamically competitive side‐reaction (4e WOR) posit as thresholds for the 2e WOR. We herein report a custom‐crafted covalent triazine network possessing strong oxidizing properties as a proof‐of‐concept metal‐free functional organic network electrocatalyst for catalyzing 2e WOR. As the first‐of‐its‐kind, the material shows a maximum of 89.9 % Faradaic Efficiency and 1428 μmol/h/cm2 H2O2 production rate at 3.0 V bias potential (vs reversible hydrogen electrode, RHE), which are either better or comparable to the state‐of‐the‐art electrocatalysts. We have experimentally confirmed a stepwise 2e WOR mechanism which was further computationally endorsed by density functional theory studies. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide (H2O2) plays a vital role in various industries, from healthcare and pharmaceuticals to water treatment and electronics. Its importance lies in its versatility as a powerful and green oxidizing agent and disinfectant. However, with an anticipated increase in demand for H2O2, greener production methods are required. Photocatalytic H2O2 generation (from O2 and/or H2O) using Metal–Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) has emerged as a sustainable alternative to traditional methods. This review provides a comprehensive overview of the intrinsic characteristics of MOFs and COFs, focusing on strategies to enhance light harvesting, charge separation, charge mobility, and the associated oxidation and reduction reactions. By addressing current limitations, this review elucidates the fundamental physicochemical properties of these materials, explores H2O2 production mechanisms, and outlines future directions for improved photocatalytic performance. [ABSTRACT FROM AUTHOR]

High-performing catalysts for the hydrogen evolution reaction (HER) via water electrolysis are of great importance for producing carbon-free green fuels. Compared to the routinely used metal-based systems under acidic conditions, metal-free pH-universal HER catalysts are smarter options taking into account the practical usability, sustainability, biocompatibility, and nominal cytotoxicity. Herein, we present an indigo-based organic conjugated porous polymer featuring a pronounced 2D few-layered morphology with surface-decorated hydrogen bonding sites for a deep catalyst–water contact and promising electrochemical HER activity. Indigo, being a vat dye, reduces in situ to its anionic leuco analogue and further promotes catalytic activity. The material manifested equipotent activity in acidic, alkaline, and neutral media superior to the contemporary metal-free carbonaceous electrocatalysts and comparable to the state-of-the-art metal-based catalytic systems. Under appropriate conditions, the material showed an overpotential of only 28 mV at 10 mA cm−2 current density. [ABSTRACT FROM AUTHOR]

The photocatalytic oxygen reduction reaction (ORR) towards hydrogen peroxide (H2O2) is a promising but challenging alternative to the industrial anthraquinone process. Crystalline porous covalent organic frameworks (COFs), a new generation of semiconductors, have attracted significant attention because they exhibit broad visible-light harvesting, possess tunable energy levels, and facilitate facile separation and migration of photogenerated charge pairs. The modulation of the energy levels of COFs could facilitate charge transport, resulting in better photocatalytic performance. Herein, the π-conjugation system of COFs was extended via a post-sulfurization process, leading to a considerably enhanced photocatalytic activity. During the sulfurization process, imine-linked COFs were converted into thiazole-linked COFs to extend the conjugation structure of COFs in the x and y directions, resulting in higher transport of electrons. The thiazole-linked 4PE-N-S presents the best photocatalytic H2O2 generation performance with a rate of 1574 μmol g−1 h−1, which is about 5.8 and 3.7 times higher than that of imine-linked 4PE-N and 4PE-TT, respectively. Our findings provide new prospects for the design and synthesis of highly active organic photocatalysts for solar-to-chemical energy conversion. [ABSTRACT FROM AUTHOR]

A facile, single-step development strategy of a sub-nanoscopic Lewis acidic Co and basic imidazole grafted porous organic polymer is reported. The synergistic activation of an epoxide and CO2 by the Lewis pairs present in the material manifested their rapid conversion to cyclic carbonates under ambient pressure with high yield, selectivity, and TOF. [ABSTRACT FROM AUTHOR]