Undoped Layered Perovskite Oxynitride Li(2)LaTa(2)O(6)N for Photocatalytic CO(2) Reduction with Visible Light

Oxynitrides are promising visible‐light‐responsive photocatalysts, but their structures are almost confined with three‐dimensional (3D) structures such as perovskites. A phase‐pure Li(2)LaTa(2)O(6)N with a layered perovskite structure was successfully prepared by thermal ammonolysis of a lithium‐rich oxide precursor. Li(2)LaTa(2)O(6)N exhibited high crystallinity and visible‐light absorption up to 500 nm. As opposed to well‐known 3D oxynitride perovskites, Li(2)LaTa(2)O(6)N supported by a binuclear Ru(II) complex was capable of stably and selectively converting CO(2) into formate under visible light (λ>400 nm). Transient absorption spectroscopy indicated that, as compared to 3D oxynitrides, Li(2)LaTa(2)O(6)N possesses a lower density of mid‐gap states that work as recombination centers of photogenerated electron/hole pairs, but a higher density of reactive electrons, which is responsible for the higher photocatalytic performance of this layered oxynitride.