One-Dimensional Single-Crystal Mesoporous TiO 2 Supported CuW 6 O 24 Clusters as Photocatalytic Cascade Nanoreactor for Boosting Reduction of CO 2 to CH 4 .

Constructing nanoreactors with multiple active sites in well-defined crystalline mesoporous frameworks is an effective strategy for tailoring photocatalysts to address the challenging of CO ₂ reduction. Herein, one-dimensional (1-D) mesoporous single-crystal TiO ₂ nanorod (MS-TiO ₂ -NRs, ≈110 nm in length, high surface area of 117 m ² 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 TiO ₂ 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 TiO ₂ nanoreactors exhibit a high-photocatalytic CO ₂ reduction selectivity to CO (95.1%). Furthermore, photocatalytic cascade nanoreactors by in situ incorporation of CuW ₆ O ₂₄ (W-Cu) clusters onto MS-TiO ₂ -NRs via O _v are designed and synthesized, which improved the CO ₂ adsorption capacity and achieved two-step CO ₂ -CO-CH ₄ photoreduction. The second step CO-to-CH ₄ reaction induced by W-Cu sites ensures a high generation rate of CH ₄ (420.4 µmol g ^-1 h ^-1 ), along with an enhanced CH ₄ 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.
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