Microwave-driven cascaded ligand-to-metal charge-transfer relays in MOFs for photothermal methanol-to-hydrogen evolution

Microwave-enabled coordination reconstruction creates Ni–O–Sn–N motif in MOFs. • Ni sites and Sn relay nodes promote a short-range N→Sn→O→Ni LMCT pathway. • The electron-relay architecture enhances charge transfer and suppresses recombination. • Ni-Sn/e-NH 2 -UiO-66 delivers 293.6 mmolg cat −1 h −1 H 2 production with < 1% CO. • Operando studies and DFT support a formate-mediated photothermal reforming pathway. Engineering efficient ligand-to-metal charge transfer (LMCT) pathways in metal-organic frameworks (MOFs) is critical for enhancing photothermal redox catalysis but remains challenging due to limited electronic coupling between photosensitive ligands and catalytic metal centers. Here, we report a microwave-enabled coordination reconstruction strategy to construct cascaded LMCT pathways within NH 2 -UiO-66 for efficient photothermal methanol-to-hydrogen conversion. By sequentially anchoring high-density Ni sites and incorporating Sn species as electronic relay nodes, a directional N→Sn→O→Ni charge-transfer network is proposed inside the MOF scaffold. Microwave irradiation not only promotes structural polarization but also drives the formation of a strongly coupled heteroatomic coordination environment, enabling shortened electron migration distance and accelerated interfacial charge transport. The optimized Ni-Sn/e-NH 2 -UiO-66 catalyst exhibits a H 2 production rate of 293.6 mmolg Cat −1 h −1 , 13 times higher than that of the thermocatalytic counterpart, with an apparent quantum efficiency of 56.7% at 380 nm. Benefiting from synergistic photothermal activation and enhanced LMCT efficiency, methanol reforming is initiated at a low temperature of 120 °C with suppressed CO formation. This work highlights microwave-assisted LMCT cascade engineering as a versatile strategy for programming directional charge-transfer pathways in MOF-based photothermal catalytic systems. Download: Download high-res image (260KB) Download: Download full-size image Microwave irradiation is employed as a coordination-engineering tool rather than a conventional heating source, enabling the formation of a heteroatomic Ni–O–Sn–N coordination motif through stepwise installation of high-density Ni single sites and Sn relay nodes in etched NH 2 -UiO-66 framework. The resulting resulting electronically coupled architecture promotes a short-range N→Sn→O→Ni electron-relay pathway, facilitating ligand-to-metal charge transfer and electronic utilization for efficient photothermal methanol reforming.