Photoenzymatic CO2 Reduction Dominated by Collaborative Matching of Linkage and Linker in Covalent Organic Frameworks.

ABSTRACT

Artificial photoenzymatic systems based on covalent organic frameworks (COFs) provide an interesting platform for converting CO2 to value-added fuels. However, the dual roles of COFs as photocatalysts and enzyme hosts showcase contradictory preferences for structures, which poses a great challenge for their rational design. Herein, we report the collaborative matching of linkages and linkers in COFs on their ability to exert both photocatalytic activity and enzyme loading, which has been neglected until now. The linkage-dependent linker regulation pattern was elucidated, and the optimal match showed a record-breaking apparent quantum efficiency at 420 nm for photocatalytic cofactor regeneration of 13.95% with a high turnover frequency of 5.3 mmol g-1 h-1, outperforming other reported crystalline framework photocatalysts. Moreover, theoretical calculations and experiments revealed the mechanism underlying the effects of matching the linkage and linker on exciton dissociation and charge migration in photocatalysis. This newfound understanding enabled the construction of COFs with both high photoactivity and large pores closer in size to the formate dehydrogenase, achieving high loading capacity and a suitable confinement effect. Remarkably, the artificial photoenzymatic system constructed according to optimal linkage-linker matching exhibited highly efficient CO2 reduction, yielding formic acid with a specific activity as high as 1.46 mmol g-1 catalyst h-1 and good reusability, paving the way for sustainable CO2 conversion driven by visible light.