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 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.