It is of profound significance concerning the global energy and environmental crisis to develop new techniques that can reduce and convert CO 2 . To address this challenge, we built a new type of artificial photoenzymatic system for CO 2 reduction, using a rationally designed mesoporous olefin-linked covalent organic framework (COF) as the porous solid carrier for co-immobilizing formate dehydrogenase (FDH) and Rh-based electron mediator. By adjusting the incorporating content of the Rh electronic mediator, which facilitates the regeneration of nicotinamide cofactor (NADH) from NAD + , the apparent quantum yield can reach as high as 9.17 � 0.44 %, surpassing all reported NADHregenerated photocatalysts constructed by crystalline framework materials. Finally, the assembled photocatalyst-enzyme coupled system can selectively convert CO 2 to formic acid with high efficiency and good reusability. This work demonstrates the first example using COFs to immobilize enzymes for artificial photosynthesis systems that utilize solar energy to produce value-added chemicals.

Enzyme immobilization is essential to the commercial viability of various critical large-scale biocatalytic processes. However, challenges remain for the immobilization systems, such as difficulties in loading large enzymes, enzyme leaching, and limitations for large-scale fabrication. Herein, we describe a green and scalable strategy to prepare high-performance biocatalysts through in situ assembly of enzymes with covalent organic frameworks (COFs) under ambient conditions (aqueous solution and room temperature). The obtained biocatalysts have exceptional reusability and stability and serve as efficient biocatalysts for important industrial reactions that cannot be efficiently catalyzed by free enzymes or traditional enzyme immobilization systems. Notably, this versatile enzyme immobilization platform is applicable to various COFs and enzymes. The reactions in an aqueous solution occurred within a short timeframe (ca. 10-30 min) and could be scaled up readily (ca. 2.3 g per reaction).

Integrating photocatalysis and biocatalysis to fabricate photobiocatalysts for asymmetric catalysis is of great significance but remains challenging. In this work, we build a photoenzymatic platform for asymmetric catalysis using rationally designed photocatalytic porphyrinic covalent organic frameworks (COFs) as mesoporous solid carriers to immobilize wheat germ lipase (WGL). The formed WGL@COFs photobiocatalysts show high enzymatic activity and good operational stability. Attributed to the proximity effect of photocatalysts and enzymes in one system, WGL@COFs exhibit good performance and reusability for an enantioselective Mannich reaction under visible light irradiation. Notably, this asymmetric reaction with the formation of C­(sp3)–C­(sp3) bonds cannot be achieved by WGL or COFs independently. Furthermore, various characterization techniques unveil the catalytic mechanism (singlet oxygen as the main pathway of asymmetric catalysis). This work creates a general and efficient strategy using COFs as photocatalytic platforms for enzyme immobilization to fabricate photobiocatalysts that realize highly efficient photoenzymatic asymmetric catalysis.

Exploration of novel material platforms to protect biological preservatives and realize intelligent regulation during fermentation is of great significance in industry. Herein, we established an intelligent responsive platform by introducing antimicrobial biomolecules (nisin) into rationally designed covalent organic frameworks (COFs), resulting in a new type of “smart formulation”, which could responsively inhibit microbial contamination and ensure the orderly progression of the fermentation process. The encapsulated biomolecules retained their activity while exhibiting enhanced stability and pH-responsive releasing process (100% bacteriostatic efficiency at a pH of 3), which can ingeniously adapt to the environmental variation during the fermentation process and smartly fulfill the regulation needs. Moreover, the nisin@COF composites would not affect the fermentation strains. This study will pave a new avenue for the preparation of highly efficient and intelligent antimicrobial agents for the regulation of the fermentation process and play valuable roles in the drive toward green and sustainable biomanufacturing.

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