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

Abstract 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.