Tetrazine-Regulated Synthesis of Azine-Linked Covalent Organic Frameworks for Photocatalytic Cofactor Regeneration and Photoenzymatic Catalysis

Abstract

We report a tetrazine-regulated in situ hydrazine release strategy to synthesize highly crystalline azine-linked COFs (AZ-COFs) with varied central cores (triazine, cyanuric acid, benzene). The slow hydrolysis of 3,6-dimethyl-1,2,4,5-tetrazine enables controlled hydrazine generation, allowing kinetically moderated azine formation and overcoming crystallization challenges. The triazine-centered AZ-COF-1 exhibits enhanced charge separation and prolonged carrier lifetimes via efficient electronic coupling and dynamic conjugation switching, achieving an exceptionally high photocatalytic nicotinamide adenine dinucleotide (NADH) regeneration of 87.02% within 16 min. More importantly, the regenerated NADH can be directly coupled with l-glutamate dehydrogenase to drive the reductive amination of α-ketoglutarate, affording l-glutamic acid with high yield, thereby demonstrating its practical utility in photoenzymatic catalysis. This work not only establishes a simple and general strategy for the kinetically controlled synthesis of azine-linked COFs but also highlights the critical role of framework electronic structure in governing photocatalytic cofactor regeneration and downstream biotransformations, providing a promising platform for artificial photosynthesis and sustainable solar-to-chemical energy conversion.