One-Dimensional Single-Crystal Mesoporous TiO2 Supported CuW6O24 Clusters as Photocatalytic Cascade Nanoreactor for Boosting Reduction of CO2 to CH4

Constructing nanoreactors with multiple active sites in well-defined crystalline mesoporous frameworks is an effective strategy for tailoring photocatalysts to address the challenging of CO₂ reduction. Herein, one-dimensional (1-D) mesoporous single-crystal TiO₂ nanorod (MS-TiO₂-NRs, ≈110 nm in length, high surface area of 117 m² g⁻¹, and uniform mesopores of ≈7.0 nm) based nanoreactors are prepared via a droplet interface directed-assembly strategy under mild condition. By regulating the interfacial energy, the 1-D mesoporous single-crystal TiO₂ can be further tuned to polycrystalline fan- and flower-like morphologies with different oxygen vacancies (O_v). The integration of single-crystal nature and mesopores with exposed oxygen vacancies make the rod-like TiO₂ nanoreactors exhibit a high-photocatalytic CO₂ reduction selectivity to CO (95.1%). Furthermore, photocatalytic cascade nanoreactors by in situ incorporation of CuW₆O₂₄ (W–Cu) clusters onto MS-TiO₂-NRs via O_v are designed and synthesized, which improved the CO₂ adsorption capacity and achieved two-step CO₂–CO–CH₄ photoreduction. The second step CO-to-CH₄ reaction induced by W–Cu sites ensures a high generation rate of CH₄ (420.4 µmol g⁻¹ h⁻¹), along with an enhanced CH₄ selectivity (≈94.3% electron selectivity). This research provides a platform for the design of mesoporous single-crystal materials, which potentially extends to a range of functional ceramics and semiconductors for various applications.