Rh-Functionalized Donor−π–Acceptor Covalent Organic Framework for Efficient Photocatalytic Nicotinamide Cofactor Regeneration
Hao Zhao, Fei Huang, Guanhua Liu, Yunting Liu, Yujie Wang, Xinlong Liu, Chengfen Xing, Jing Gao, Xiaoyang Yue, Yanjun Jiang
Abstract
A nicotinamide adenine dinucleotide phosphate (NADPH)-mediated photoenzyme-coupled catalytic system is an attractive and green strategy for chemical conversion. However, artificial photocatalytic NADPH regeneration with low activity and selectivity has posed a challenge when it is coupled with enzyme catalysis. Therefore, we developed a strategy to prepare an “all-in-one” photocatalyst (Rh-sp 2 c-COF) by immobilizing an electron mediator ([Cp*Rh(bpy)(H 2 O)] 2+ ) in a covalent organic framework (COF) with a donor−π–acceptor structure for efficient photocatalytic NADPH regeneration. The immobilized [Cp*Rh(bpy)(H 2 O)] 2+ not only achieves specific regeneration of 1,4-NADPH but also improves the efficiency of electron transfer and utilization by constructing intramolecular electron transfer channels and electron buffer tanks. In addition, the donor−π–acceptor structure expands the range of light absorption and promotes effective carrier separation and directional transfer. The turnover frequency of NADPH regeneration by Rh-sp 2 c-COF reaches 2.17 mmol·g COF –1 ·h –1, which is 3.28, 1.99, and 4.5 times higher than those of sp 2 c-COF, sp 2 c-COF + free [Cp*Rh(bpy)(H 2 O)] 2+, and imine-COF, respectively. Finally, Rh-sp 2 c-COF coupled with ene reductase achieves efficient asymmetric hydrogenation of C═C. This work provides an approach for accurate predesign of photocatalysts to achieve efficient conversion and utilization of solar energy.