Preparation of Hydrophilic Conjugated Microporous Polymers for Efficient Visible Light-Driven Nicotinamide Adenine Dinucleotide Regeneration and Photobiocatalytic Formaldehyde Reduction

Recently, photobiocatalysis with oxidoreductases, inspired by natural photosynthesis, has drawn increasing attention due to its high catalytic efficiency and selectivity. However, although an important cofactor for the activation of redox enzymes, nicotinamide adenine dinucleotide (NADH) suffers from the drawbacks of cost and limited stability. Moreover, the design of an effective NADH regeneration system remains a huge challenge. Here, we report a visible light-driven conjugated microporous polymer DBTS-CMP1 for the heterogeneous photocatalytic regeneration of NADH. Thanks to various improved properties, such as extended visible light absorption, adequate fluorescence lifetime, enhanced wettability, and rapid charge separation and transfer, an NADH regeneration efficiency of 84% in 45 min was achieved with DBTS-CMP1. In addition, the small molecule model compound DBTS-Ph2, which shares similar structural motifs, was also designed to further study the photoinduced electron transfer process. The strong coordination interaction between dibenzo-[b,d]thiophene sulfone and the Rh metal center, as reflected in fluorescence quenching, cyclic voltammetry, and Fourier-transform infrared spectroscopy measurements, plays an essential role in electron transfer from the photocatalyst to the Rh complex, thus endowing DBTS-CMP1 with a high reaction conversion and selectivity (100%) for 1,4-NADH regeneration. Finally, a photobiocatalytic system was constructed by incorporating NADH-dependent alcohol dehydrogenase for the reduction of formaldehyde into methanol. A total amount of 2.23 mM methanol with a turnover number of 2.23 mmol g–1 was obtained after 95 min in the photobiocatalytic system, indicating the high photostability and biocompatibility of our DBTS-CMP1 photocatalyst.