Facet-dependent spatial separation of dual cocatalysts on MOF photocatalysts for H₂O₂ production coupling biomass oxidation with enhanced performance

Cooperative coupling of photocatalytic two-electron oxygen reduction reaction (2e-ORR) with oxidative organic synthesis holds great promise for sustainable production of valuable chemicals. To achieve high performance, the rational design of photocatalysts with effective electron-hole separation and redox capability is crucial. Herein, a MOF-based photocatalyst with crystal facet-dependent spatial separation of dual cocatalysts is constructed for photocatalytic 2e-ORR coupled with vanillyl alcohol oxidation reaction (VAOR). The facet-dependent growth of reductive Pd and oxidative CoO_x cocatalysts respectively on the {100} and {001} facets of MIL-125-NH₂ enables the directional migration of photogenerated carries, facilitating the charge separation for redox reactions. Additionally, the interaction between Pd and MIL-125-NH₂ modulates the Pd sites into electron-sufficient state with upshifted d-band center, promoting the O₂ activation and *OOH intermediate formation. The rationally designed composite photocatalyst delivers an excellent H₂O₂ yield of 74.8 mM g⁻¹ h⁻¹ and a high vanillic acid production rate of 80.9 mM h⁻¹ g⁻¹ with the conversion and selectivity of 96.8 % and 91.1 %, respectively.