TiO ₂ -Supported Cu-MOF Nanocomposites for Photoboosted Electrochemical CO ₂ Reduction to Methane

The photoelectrochemical reduction of carbon dioxide (PERCO2) provides an efficient and sustainable pathway to transform CO2 into value-added fuels by using solar energy. In this study, we report the rational design of TiO2-supported Cu-based metal–organic framework (Cu-MOF) nanocomposites (HKUST-1/TiO2) that integrate semiconductor and porous architectures at the nanoscale for photoboosted electrochemical conversion of CO2 to CH4. The composite was fabricated via a solvothermal method, yielding a nanoscale interface with uniformly dispersed TiO2 domains anchored onto the HKUST-1 framework, forming intimate heterojunctions with abundant Cu redox-active sites. Comprehensive structural, morphological, and spectroscopic analyses confirmed the nanostructured morphology and intimate interfacial contact, which are critical for efficient charge transfer and broadened light-harvesting capability. The optimized HKUST-1/TiO2 nanocomposite exhibits a Faradaic efficiency of ∼83 ± 2% for methane at −1.2 V vs RHE, accompanied by significant photocurrent enhancement and reduced charge transfer resistance. These superior photoelectrocatalytic properties arise from the synergistic interplay between TiO2 semiconductor nanoparticles and the porous Cu-MOF matrix, which collectively promote efficient charge separation, directional electron transport, and selective CO2 adsorption and activation. Notably, the catalyst maintains nearly 100% CH4 selectivity over 6 h of continuous operation, indicating a stable and durable performance under aqueous conditions. Postreaction analyses further confirm the preservation of crystallinity and morphological integrity. This work underscores the importance of nanoscale heterointerface engineering in optimizing photoelectrocatalytic CO2 conversion and establishes TiO2-Cu-MOF nanocomposites as robust, cost-effective materials for solar-driven carbon mitigation and renewable fuel generation.