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.
Organometallic Lewis acids play an important role in modern organic synthesis. How to design and synthesize highly efficient and recyclable organometallic Lewis acid catalysts that can be conveniently applied in chemical reactions are key issues for sustainable synthetic processes. In general, stronger acidity means higher catalytic activity for organometallic Lewis acids. However, with the rise in acidity, the compound becomes more susceptible to hydrolysis and cannot be recycled. Simultaneous improvement of the hygroscopic character and Lewis acidity/catalytic activity of organometallic Lewis acids is highly desirable from the standpoint of practical applications. In this mini-review, the history of air-stable organometallic Lewis acids is introduced, with emphasis on our research works on metallocene, organobismuth, and organoantimony Lewis acids to the aspects of synthesis, characterization and catalytic application in carbon-carbon bond (Friedel-Crafts acylation, Mukaiyama aldol reactions; allylation, cyclotrimerization, Mannich reactions, cross-condensation reactions) and carbon-heteroatom bond (acylation, S-S bond cleavage, glycosylation) formation reactions. In terms of stability, storage, versatile ability, high catalytic activity and chemo-/stereoselectivity, the complexes will find broad applications in organic synthesis.
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