Dynamic Soft-Confinement via Hydrogen-Bonded Organic Frameworks Reshapes C-C Coupling Interfacial Chemistry at Bi1-Bi2 Sites.

The core bottleneck in photocatalytic CO2 reduction toward multi-carbon oxygenates lies in the thermodynamic-kinetic dual limitations of the C-C coupling step. Conventional strategies have focused on intrinsic electronic structure optimization of active sites while overlooking the critical influence of the reaction microenvironment on coupling probability. Herein, we propose a dynamic soft-confinement catalytic strategy by in situ constructing a disordered hydrogen-bonded organic framework (HOF) layer on Bi3O4Br surfaces, thereby establishing an HOF/Bi3O4Br integrated photocatalytic system. The introduction of HOF not only induces the formation of asymmetric Bi1-Bi2 coupling sites but also establishes a dynamic hydrogen-bonding microenvironment surrounding them. This microenvironment enhances CO2 coverage near the coupling sites by constructing a persistent carbon source enrichment layer. Simultaneously, the interfacial polarization field promotes exciton dissociation and directs electron transport toward the Bi1-Bi2 sites. Furthermore, the reconfigurable hydrogen bonds impose orientational soft confinement on *CO intermediates, guiding them into spatial configurations favorable for *OCCO bond formation. This soft-hard synergistic interfacial design enables 0.7HOF/Bi3O4Br to achieve a CH3COOH production rate of 325.12 µmol g-1 h-1 with 98.81% product selectivity under sacrificial agent-free conditions. This work demonstrates that dynamic microenvironment programming around active sites constitutes a critical pathway for overcoming the photocatalytic C-C coupling bottleneck.