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Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions
Published on: October 5, 2019
Regioisomerism in covalent organic frameworks for near-infrared-light-driven photocatalytic hydrogen peroxide
Zhongwei Liu1, Yaxin Qin2, Xu Ding3
1School of Chemistry and Chemical Engineering, Hainan University, Haikou 570228, China; Key Laboratory of Functional Molecular Solids of Ministry of Education, Anhui Basic Discipline Research Center for Clean Energy and Catalysis, College of Chemistry and Materials Science, Anhui Normal University, Wuhu 241002, China.
Abstract:
Near-infrared (NIR) photocatalysis is attractive for chemical conversion due to its lower photon energy, reduced side reactions, deeper penetration, and greater solar abundance. However, constructing covalent organic frameworks (COFs) capable of effectively harvesting NIR light for fuel and chemical production, particularly for photocatalytic hydrogen peroxide (H2O2) production, remains a critical hurdle. Herein, a regioisomerism regulation strategy is employed to modulate the relative positions of nitrogen (N) and sulfur (S) atoms in the thiazole ring of two-dimensional (2D) thiazole-based COFs. This achieves successful tuning of the electronic structure by enhancing the extent and continuity of the π-conjugation throughout the framework, achieving NIR light absorption up to 1500 nm for the thiazole-based COF-BT5. This, combined with the enhanced photogenerated charge separation, enables 5,5'-bithiazole-based COF-BT5 to photosynthesize H2O2 from pure water at a record-high rate of 1758 μmol g-1 h-1 under 810 nm irradiation, which is about 2.4-fold higher than that of the 4,4'-bithiazole-based COF-BT4 under identical conditions and surpassing most reported NIR-responsive catalysts. Moreover, COF-BT5 achieves a H2O2 production rate of 15,849 μmol g-1 h-1 under full-spectrum irradiation without sacrificial agents. This work provides a regioisomerism regulation strategy for tuning the electronic structure of 2D COFs, thereby addressing limitations in NIR-driven chemical transformations and expanding the applicability of COF-based photocatalysis.
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