Chromate Intercalation in ZnTi-LDH for Highly Selective and Efficient Photocatalytic Methane Oxidation to Oxygenates

The highly selective photocatalytic oxidation of methane (CH 4 ) to oxygenates remains challenging due to over-oxidation and low efficiency. Herein, a series of chromate-intercalated ZnTi-layered double hydroxide (CrO 4 2- -ZnTi-LDH, CZT-x) photocatalysts were constructed via a combined hydrothermal and anion-exchange method. Under simulated solar irradiation, the optimized CZT-30 catalyst achieves a remarkable oxygenates production rate of 2603.60 μmol·g -1 ·h -1 , which is 1.67 times higher than that of the pristine ZnTi-LDH, with nearly 100% selectivity. This high selectivity (>92%) is well maintained over a 9-hour duration. Structural and spectroscopic analyses reveal that the intercalated CrO 4 2- anions not only modulate the interlayer microenvironment and host electronic structure but also enhance light absorption and charge separation efficiency. In-situ EPR and Raman spectroscopy revealed that the CrO 4 2- intercalation serves a dual function: it selectively boosts the generation of the key *OOH intermediate and enhances the hole-mediated activation of *CH 4 to *CH 3 . This synergistic effect promotes the coupling of *CH 3 and *OOH, leading to the highly selective production of oxygenates. This work provides a strategy for designing efficient LDH photocatalysts for selective methane valorization.