Efficient Photocatalytic Reduction of CO₂ to CO Using NiFe₂O₄@N/C/SnO₂ Derived from FeNi Metal-Organic Framework

Use of light is considered an effective approach to convert CO₂ into usable chemical energy. In the present study, an iron- and nickel-containing bimetallic metal-organic framework (MOF) was synthesized via a simple solvothermal route. SnO₂ was then composited with the said MOF, and the obtained material was calcined and annealed to fabricate a series of nanophotocatalysts. The annealed sample displayed superior photocatalytic activity to the calcined sample, possibly due to the carbon-nitrogen layer formed after annealing mediating the charge-transfer process. The results of photocatalytic experiments indicated that using [Ru(bpy)₃]Cl₂·6H₂O as a photosensitizer and triethanolamine (TEOA) and acetonitrile (MeCN) as sacrificial agents, the catalyst sample was annealed at 450 °C (NiFe₂O₄@N/C/SnO₂-450) to afford the highest CO yield from CO₂ (2057.41 μmol g^-1 h^-1). The increase in the photocatalytic ability of the nanocomposites is basically attributed to multiple synergistic effects between NiFe₂O₄ and SnO₂, which reduce the recombination probability of the photo-induced electrons and holes. Ultimately, a photocatalytic reaction mechanism is proposed for NiFe₂O₄@N/C/SnO₂ in the reduction of CO₂.