Interfacial polarization via spatially directed charge transfer at Cu/Co heterojunction for dual-enhanced CO2 photoreduction and biomass refining

Coupling photocatalytic CO 2 reduction with biomass refining offers a sustainable route to produce renewable fuels and value-added chemicals. However, interfacial charge recombination limits its efficiency. Herein, we report a three-dimensional, hierarchical, honeycomb-like carbon nitride framework co-doped with Cu/Co species (Cu x Co y @CN) and enriched with N vacancies, synthesized through a sequential hydrothermal-calcination and in-situ doping strategy. Advanced spectroscopy and in-situ probes reveal the directional electron transfer from Co to Cu sites, creating an electron-rich heterointerface that spatially separates redox centers, namely Cu sites for CO 2 reduction and Co sites for biomass oxidation. The engineered architecture delivers a larger specific surface area (95.40 m 2  g −1 ), extended visible-light absorption (>800 nm), narrowed band gap (to 1.93 eV), and enhanced charge separation (2.27-fold higher photocurrent). The optimized Cu 2 Co 1 @CN catalyst achieves an exceptional CO evolution ratio of 84.8 μmol g −1  h −1 with a xylonic acid yield of 74.0% from xylose, and retains 91.8%/95.2% of its initial CO/xylonic acid activity after eight cycles. Furthermore, the Cu 2 Co 1 @CN catalyst shows broad substrate scope and promising scalability, including sunlight-tracking experiments. This study provides fundamental insights into interfacial charge engineering and presents a viable strategy for synergistically converting solar energy, abundant biomass, and anthropogenic CO 2 into sustainable chemical feedstock.