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 H 2 O 2 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-NH 2 significantly enhances the H 2 O 2 production. The introduction of -OMe groups induces lattice distortion in UIO-66-NH 2 , resulting in the change of proton donor for the protonation of OOH* intermediate from -COOH to -NH 3 + 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-NH 2 is also enhanced, evidenced by rotating ring-disk electrode test and theoretical calculation. As a result, an improved photocatalytic ability is achieved with an H 2 O 2 yield of 312.9 mM g -1 h -1 , ~4.7 times higher than that of the original UIO-66-NH 2 . • Substitution of electron-donating groups induces lattice distortion in MOF. • The lattice distortion and electron-donating effect in photocatalysis are unveiled. • Lattice distortion optimizes the protonation pathway of intermediate OOH*. • Electron-donating effect promotes light harvesting and charge separation. • Enhanced performance is achieved with a remarkable H 2 O 2 yield of 312.9 mM g -1 h -1 .