Hollow Rh-COF@COF S-Scheme Heterojunction for Photocatalytic Nicotinamide Cofactor Regeneration
Hao Zhao, Lirong Wang, Guanhua Liu, Yunting Liu, Suoqing Zhang, Lihui Wang, Xiaobing Zheng, Liya Zhou, Jing Gao, Jiafu Shi, Yanjun Jiang
Abstract
Photocatalytic regeneration of a nicotinamide cofactor, nicotinamide adenine dinucleotide phosphate (NADPH), has emerged as an ideal cascade partner for combination with enzymatic transformations, but it still suffers from low efficiency due to the recombination of photogenerated charge carriers. Herein, a hierarchical Rh-covalent organic framework (COF)@COF core–shell hollow sphere (CSHS) with S-scheme heterojunction is proposed to enhance the charge carrier transfer and utilization in photocatalysis to regenerate the expensive NADPH. The hierarchical Rh-COF Bpy @ hollow spherical COF (HCOF) CSHS was prepared by simple sequential in situ growth. The turnover frequency of Rh-COF Bpy @HCOF 25 for NADPH regeneration reached 2.6 mmol·g Rh-COF –1 ·h –1, which was 3.7 times that of pure Rh-COF Bpy under visible light. Density functional theory calculation and X-ray photoelectron spectroscopy analysis showed that an internal electric field directed from Rh-COF Bpy to HCOF was formed in Rh-COF Bpy @HCOF CSHS, which accelerated the photogenerated electron transfer from HCOF to Rh-COF Bpy . In situ irradiated XPS analyses and photoirradiated Kelvin probe measurement revealed the S-scheme charge-transfer mechanism within Rh-COF Bpy @HCOF. The Rh-COF Bpy @HCOF photocatalytic NADPH regeneration system was further coupled with enzymatic reduction of C═C, achieving a photoenzyme cascade reaction. This work provides a protocol for the design and utilization of COF-based artificial photosynthetic systems.