Reduced graphene oxide/NH₂-MIL-125(Ti) composite: Selective CO₂photoreduction to methanol under visible light and computational insights into charge separation

The development of visible-light active photocatalysts is highly desirable for CO2 reduction to hydrocarbons and alcohols using sunlight. Here, we report the metal-organic frameworks (MOF) of amino-benzene dicarboxylate with titanium oxocluster center (NH2-MIL-125(Ti)) and modified with reduced graphene oxide (RGO), RGO-NH2-MIL-125(Ti), ideal for the visible-light-driven photocatalytic reduction of CO2 to hydrocarbons and methanol. The catalyst provides high quantum efficiency and selectivity for methanol. The cluster model and self-consistent charge density functional tight binding methods were used to investigate the photogenerated charge separation for NH2-MIL-125(Ti). The quantum modelling suggests that holes were accumulated in the central ring Ti8O8(OH)4, where strongly adsorbed electron donor, triethanolamine, undergoes photooxidation while electrons were located in the organic ligand of MOF including the NH2 group. The binding affinity of NH2 reaction sites to CO2 possibly work to improve the photocatalytic reduction of CO2 to methanol. The RGO also play an important role for charge separation and better photocatalytic reduction with RGO-NH2-MIL-125(Ti).