Decoupling CO2 Availability from Bulk Solubility via Biohybrid Reaction-Diffusion Nanoconfinement.

Although contemporary CO2 reduction research is largely dominated by the search for novel active sites, the performance of even the most sophisticated catalysts remains fundamentally constrained by the sluggish mass transport of dissolved CO2. Here, we demonstrate that engineering the local chemical microenvironment is as critical as tuning intrinsic catalytic activity. Inspired by the functional orchestration of cyanobacterial carboxysomes, we report a biomimetic interface that integrates carbonic anhydrase within copper phosphate nanoflowers to establish a reaction-diffusion nanoreactor. Hyperspectral micro-FTIR imaging reveals a spatially localized and quantitatively enhanced CO2-associated signal at the biohybrid interface, consistent with the formation of an interfacial CO2 reservoir sustained by enzymatic bicarbonate dehydration. This interfacial CO2 enrichment directly translates into enhanced carbon utilization, manifested by higher conversion rates and improved selectivity toward carbon-derived reduction products relative to the enzyme-free control. Real-time online electrochemical mass spectrometry confirms a shift in selectivity toward carbon-derived products under conditions where conventional electrodes are transport-limited. This work establishes that shifting the focus from material-bound kinetics to interface-driven carbon management is also a strategy for advancing electrosynthesis.