Unveiling the lattice distortion and electron-donating effects in methoxy-functionalized MOF photocatalysts for H₂O₂ production

Semiconducting metal-organic frameworks (MOFs) are emerging photocatalysts for H₂O₂ production via the two-electron oxygen reduction (2e-ORR) process. Whether and how the functional groups on MOF nodes affect the 2e-ORR mechanism and performance remain largely unexplored. Herein, we report that partial replacement of formate (-COO^-) by methoxy (-OMe) coordinated Zr-oxo cluster in UIO-66-NH₂ significantly enhances the H₂O₂ production. The introduction of -OMe groups induces lattice distortion in UIO-66-NH₂, resulting in the change of proton donor for the protonation of OOH* intermediate from -COOH to -NH₃⁺ with a lowered kinetic energy barrier. The -OMe groups with electron-donating effect contribute to promoted light harvesting and charge separation. The 2e-ORR selectivity of -OMe functionalized UIO-66-NH₂ is also enhanced, evidenced by rotating ring-disk electrode test and theoretical calculation. As a result, an improved photocatalytic ability is achieved with an H₂O₂ yield of 312.9 mM g⁻¹ h⁻¹, ~4.7 times higher than that of the original UIO-66-NH₂.