Controllable Synthesis of MIL-101(Cr)@TiO₂ Core–Shell Nanocomposites for Enhanced Photocatalytic Activity

Incorporating high surface area and high CO 2 adsorption capacity of metal–organic frameworks (MOFs) together with highly efficient semiconductor photocatalysts provides an ideal strategy for designing CO 2 reduction photocatalysts. Controllable growth of TiO 2 nanoparticles on MIL-101(Cr) can be obtained and yields MIL-101(Cr)@TiO 2 core–shell photocatalysts via a fluoride-assisted solvothermal method. Corrosion occurs on the surface of MIL-101(Cr) by the action of F – and generates an activated surface, facilitating the growth of a TiO 2 shell. MIL-101(Cr)@TiO 2 nanocomposites with different TiO 2 contents are remarkably fabricated by controlling the reaction conditions. The morphology, structure, surface area, and composition of the as-prepared MIL-101(Cr)@TiO 2 nanocomposites are investigated by various characterization methods. The EDS mapping images reveal that the Ti and O elements are uniformly distributed on the shell, but Cr and C elements are mainly situated at the core of the composite, which further indicates the successful synthesis of the MIL-101(Cr)@TiO 2 core–shell structure. The photocatalytic conversion of CO 2 into CH 4 is noticeably enhanced by the produced MIL-101(Cr)@TiO 2 octahedra inheriting both large surface area (387.3 m 2 g –1 ) and high CO 2 adsorption capacity. Compared to pure TiO 2 nanoparticles under the same conditions, the optimized MIL-101(Cr)@TiO 2 photocatalyst exhibits a much greater CO 2 conversion efficiency, with a CH 4 generation rate of 0.22 μmol h –1 g –1 . This work will advance the experimental and theoretical basis for exploring highly efficient CO 2 reduction photocatalysts.