Constructing Synergistic Triazine and Acetylene Cores in Fully Conjugated Covalent Organic Frameworks for Cascade Photocatalytic H₂O₂ Production

Abstract

Covalent organic frameworks (COFs) are an ideal template for photocatalytic H 2 O 2 synthesis because of the tunable chemical structures and semiconductor properties. However, the photoactivity for COFs is still under-improved due to the inefficient intrinsic charge generation, fast recombination of photogenerated charges, and limited electron transport along the frameworks. Herein, spatially separated and synergistic triazine and acetylene units are first integrated into COFs (EBA-COF and BTEA-COF) for photocatalytic H 2 O 2 production. The spatial separation of triazine and acetylene cores leads to efficient charge separation and suppressed charge recombination, and CC linkage facilitates electrons transport over the skeletons. Both experimental and computational results suggested that triazine and acetylene units synergistically promote H 2 O 2 synthesis in a two-electron pathway. The EBA-COF showed an attractive activity with a H 2 O 2 production rate of 1830 μmol h −1 g cat −1 , superior to that of most other COF-based catalysts. This study provides a method for designing photocatalysts with synergistic photocatalytic active sites based on vinylene-linked COFs.

Porphyrin-based conjugated organic polymer with dual metal sites for highly active and selective visible-light-driven reduction of CO2to CO

“…The geometries of the two models were optimized without any restriction, and the electrostatic potential surfaces were calculated at the theoretical level of B3LYP/def2-SVP, which is reliable for the current catalytic reaction. 34 The model of CuTBPP-BPY-COP is an open-shell system. Consequently, an unrestricted theoretical method was adopted; the calculated energies of the HOMO and LUMO were −5.39 and −2.36 eV, respectively.…”

Conjugated Organic Polymers with Anthraquinone Redox Centers for Efficient Photocatalytic Hydrogen Peroxide Production from Water and Oxygen under Visible Light Irradiation without Any Additives

“…Meanwhile, the restricted variability of inorganic materials is disadvantageous for the decoration of photoelectric properties, band structures, and external active sites according to the specific reaction . In addition, the quick recombination of photo-induced electrons and holes as well as the low surface area have significantly inhibited the substrate molecules’ adsorption/activation and subsequent photocatalytic conversion . Hence, the design and development of new photocatalytic systems with specific structures and properties that enable efficient adsorption/activation of H 2 O and O 2 molecules, promote charge separation/migration, and extend visible light absorption are highly desirable for realizing efficient photocatalytic H 2 O 2 production.…”

“…With constant efforts, a variety of COP-based photocatalytic systems with outstanding structures and properties have been developed rapidly, which can promote efficient O 2 reduction to generate H 2 O 2 . However, the photocatalytic efficiency is relatively low when inorganic sacrificial agents (ethyl alcohol, ascorbic acid, and triethanolamine) are used. ,, Several strategies have been employed to enhance photocatalytic activity such as creating donor–acceptor dyads, doping heteroatoms, forming heterojunctions, and so forth, ,, but the lack of specific redox centers is still the main reason for low photocatalytic H 2 O 2 generation efficiency from H 2 O and O 2 in net water without any additives.…”

“…26 In addition, the quick recombination of photo-induced electrons and holes as well as the low surface area have significantly inhibited the substrate molecules' adsorption/activation and subsequent photocatalytic conversion. 27 Hence, the design and development of new photocatalytic systems with specific structures and properties that enable efficient adsorption/activation of H 2 O and O 2 molecules, promote charge separation/migration, and extend visible light absorption are highly desirable for realizing efficient photocatalytic H 2 O 2 production. Conjugated organic polymers (COPs) with semiconductor properties have attracted extensive interest as a complement to the inorganic counterpart due to their high surface area, tunable photoelectric responsiveness, and extended π-conjugated structure.…”

“…34 However, the photocatalytic efficiency is relatively low when inorganic sacrificial agents (ethyl alcohol, ascorbic acid, and triethanolamine) are used. 27,33,35 Several strategies have been employed to enhance photocatalytic activity such as creating donor− acceptor dyads, doping heteroatoms, forming heterojunctions, and so forth, 26,36,37 38 although the conventional anthraquinone method is criticized due to the involvement of substantial energy input, severe environmental contamination, and significant safety issues. 12 Attractively, the synthesis mode modules of COPs enable homogeneous incorporation of anthraquinone moieties into π-conjugated frameworks by deliberate selection of building blocks including anthraquinone at the molecular level.…”