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

Incorporating high surface area and high CO₂ adsorption capacity of metal–organic frameworks (MOFs) together with highly efficient semiconductor photocatalysts provides an ideal strategy for designing CO₂ reduction photocatalysts. Controllable growth of TiO₂ nanoparticles on MIL-101-(Cr) can be obtained and yields MIL-101-(Cr)@TiO₂ 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 TiO₂ shell. MIL-101-(Cr)@TiO₂ nanocomposites with different TiO₂ contents are remarkably fabricated by controlling the reaction conditions. The morphology, structure, surface area, and composition of the as-prepared MIL-101-(Cr)@TiO₂ 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)@TiO₂ core–shell structure. The photocatalytic conversion of CO₂ into CH₄ is noticeably enhanced by the produced MIL-101-(Cr)@TiO₂ octahedra inheriting both large surface area (387.3 m² g^–1) and high CO₂ adsorption capacity. Compared to pure TiO₂ nanoparticles under the same conditions, the optimized MIL-101-(Cr)@TiO₂ photocatalyst exhibits a much greater CO₂ conversion efficiency, with a CH₄ generation rate of 0.22 μmol h^–1 g^–1. This work will advance the experimental and theoretical basis for exploring highly efficient CO₂ reduction photocatalysts. [ABSTRACT FROM AUTHOR]