Hydrogen-Bonded Organic Frameworks (HOFs) for NADH Regeneration and Enzymatic Hydrogenation: HOF-in-HOF Artificial Photosynthetic System for Solar-to-Chemical Conversion.

The efficiency of artificial photosynthesis lies not only in the catalysts themselves, but also in the spatiotemporal landscape for efficient mass-energy coupling, which is governed by electron, proton, and molecule transfer. Herein, we propose a scaffold engineering strategy to construct an enzyme-photo-membrane coupled artificial photosynthetic system (epmCAPS) within HOF-in-HOF architecture for NADH regeneration and enzymatic hydrogenation, where enzyme-loaded HOF particles for substrate conversion are encapsulated within photocatalytic HOF capsular membranes for cofactor regeneration. This unique configuration enables independent and synergistic regulation of electron, proton, and NADH transfer by modulating the electronic structure of the capsule (via benzene ring units), proton relay (via carboxylate group density), and mass diffusion path (via enzyme-photocatalyst distance), respectively. The system achieves a record initial NADH regeneration rate of 28.23 ± 0.62 mmol g h with a 22.13% apparent quantum yield. When applied to solar-driven lactate synthesis, the epmCAPS achieves a solar-to-chemical conversion efficiency of 7.27 ± 0.34%-a nearly threefold higher than previous records. Furthermore, we demonstrate the generality of this platform by synthesizing a spectrum of C-C chemicals, including methanol and mannitol, while maintaining stable operation for over 6 h. Our work delivers a blueprint for the next-generation artificial photosynthetic systems for sustainable energy and green chemical production.