Selective CO ₂ ‐to‐CH ₄ Photoreduction Enabled by Au/TiO ₂ ‐ V Ti Nanosheets via Boosting H ₂ O Dissociation and CO Protonation

Photocatalytic CO 2 methanation is fundamentally constrained by two intertwined bottlenecks: inefficient proton generation from H 2 O dissociation and the premature desorption of the critical * CO intermediate. Here, we design metal cation vacancy clusters‐O − motifs for accelerating H 2 O dissociation and boosting * CO protonation, while supported metal sites for CO 2 activation over metal‐anchored metal oxide nanosheets. As a prototype, we fabricate Au/TiO 2 ‐ V Ti nanosheets, where synchrotron‐radiation X‐ray absorption fine structure and electron paramagnetic resonance spectroscopy confirm V Ti ‐O − and coordination‐unsaturated Au sites. Density‐functional‐theory calculations reveal the creation of V Ti ‐O − sites drive the step of * CO protonation toward * CHO from an endothermic process (0.09 eV) to an exothermic one (−0.29 eV), and concurrently the energy for H 2 O dissociation into protons is lowered by a factor of two (1.31 eV → 0.65 eV). In situ Fourier‐transform infrared spectroscopy directly captures a distinct * CO intermediate, confirming its stabilization on the photocatalyst surface and thereby promoting the protonation step toward * CHO. Consequently, the Au/TiO 2 ‐ V Ti nanosheets show a superior CH 4 formation rate of 156.5 µmol g −1 h −1 with near‐100% selectivity. Briefly, this work offers key insights into CO 2 methanation bottlenecks and proposes a catalyst design blueprint to advance CO 2 valorization.