Photocatalytic Synergy Between α-Bi₂O₃ Nanosphere and Spindle MIL-88A for Gas-Phase CO₂ Reduction

Visible light-active photocatalysts play a crucial role in gas-phase photocatalytic CO₂ reduction, offering significant potential for sustainable energy conversion. Herein, we present the synthesis of spindle-shaped Iron (Fe)-based metal-organic framework (MOF) MIL-88 A, coupled with distinct α-Bi₂O₃ nanospheres. The α-Bi₂O₃/MIL88A heterostructure is formed by interacting opposite surface charges, enhancing visible-light absorption and efficient interfacial charge-carrier separation. Such low-cost photocatalysts have a 1.75 eV band gap and demonstrate enhanced efficacy in converting CO₂ to CO, CH₄, and H₂ in water without using any sacrificial agents or noble metals compared to pristine MIL88A. In addition, in-situ Electron Spin Resonance (ESR) analyses revealed that these unique catalysts combination promoted enhanced interfacial charge dynamics, creating efficient trapping sites for photogenerated carriers. Further, in-situ Diffuse Reflectance Infrared Fourier Transfer Spectroscopy (DRIFTS) investigation elucidates the plausible reaction mechanism and provides an effective methodology for catalyst screening for CO₂ photoreduction. This study offers an effective approach for synthesizing the earth-abundant heterostructure from metal oxide and low-cost MOFs, enhancing photocatalytic activity for sustainable carbon dioxide conversion into invaluable chemicals.