Synergy of Electron Transfer and Electron Utilization via Metal–Organic Frameworks as an Electron Buffer Tank for Nicotinamide Regeneration

• Published in: ACS catalysis 2020-03, Vol.10 (5), p.2894-2905
• Main Authors: Wu, Yizhou, Shi, Jiafu, Li, Donglin, Zhang, Shaohua, Gu, Bo, Qiu, Qian, Sun, Yiying, Zhang, Yishan, Cai, Ziyi, Jiang, Zhongyi
• Format: Article
• Language: English
• ISSN: 2155-5435; 2155-5435
• DOI: 10.1021/acscatal.9b05240

Solar energy conversion by photocatalysis holds promise in energy supply, but its efficiency is hindered by the mismatch in charge generation, transfer, and utilization. In natural photosynthesis, photosystem I (PSI) exhibits an intrinsic quantum efficiency of nearly 100% in solar energy conversion. The elaborate synergy of electron transfer and electron utilization guarantees the conversion of unstable excited electrons to stable electrons in reduced nicotinamide adenine dinucleotide phosphate (NADPH). To demonstrate this in vitro, we report a design of core–shell metal–organic frameworks (MOFs) as an “electron buffer tank” to coordinate electron transfer and electron utilization in photocatalysis. The electrons are generated via the irradiation on photosensitizers (2-aminoterephthalic acid, NH2-BDC) in the core and then transferred to Zr6O8 clusters on the shell through the light-induced ligand-to-metal charge transfer mechanism. Neighboring reaction centers, [Cp*Rh­(bpydc)­H2O]2+, on the MOFs behave as the electron buffer tank and store these electrons in the form of hydrides for subsequent regeneration of reduced nicotinamide adenine dinucleotide (NADH). The electron lifetime is prolonged from nanoseconds to seconds, leading to 2.27-fold enhancement of electron availability and 2.08-fold enhancement of activity compared to the homogeneous reaction counterpart. The coupling of NADH regeneration and enzyme catalysis further enables the asymmetric reduction of carbonyl to chiral amine. The electron buffer tank concept may offer a generic strategy to coordinate mass transfer and chemical reaction in a broad range of catalytic processes.