Modular Assembly of a Biocatalytic Material for Stereoselective C─Si Bond Formation.

Biocatalysis offers sustainable routes to complex molecules, yet translating enzymatic activity into robust, reusable materials remains a major challenge. Here, we report the modular assembly of a self-supporting biocatalytic material for stereoselective C─Si bond formation using an engineered Rhodothermus marinus cytochrome c (CC). The material was constructed by site-specific covalent coupling of CC fused with two SpyCatcher domains (SC-CC-SC) with streptavidin variants bearing SpyTag domains (STV-ST), yielding a red, porous enzyme foam with defined hexagonal architecture. The modular STV-mediated crosslinking strategy enables the formation of carrier-free materials with high enzyme density and minimal diffusion barriers. The CC foams retained structural integrity and catalytic activity after drying, catalyzing the formation of a chiral organosilicon compound with high enantioselectivity under mild conditions. The enzyme remains active at the extensive gas-liquid interfaces within the foam, effectively combining high catalyst loading with excellent mass transport. The resulting material retains high stereoselectivity (>95% ee), exhibits catalytic performance comparable to previously reported carrier-based immobilization approaches, and maintains catalytic activity over five consecutive reuse cycles. This immobilization concept establishes a generalizable platform for fabricating biocatalytic materials from monomeric enzymes and expands the scope of enzymatic C─Si bond formation toward scalable, sustainable synthesis.