Abstract: Highly active and selective photocatalytic oxidation of methane (CH₄) to methanol (CH₃OH) remains challenging because of the high C-H bond dissociation energy, CH₃OH overoxidation, and limited mass transport in conventional nonporous or microporous catalysts. Herein, a facile hydrothermal strategy was developed to synthesize hierarchical TS-1 photocatalysts with in situ encapsulated ultrasmall AuPd nanoalloys (~2 nm). The obtained catalysts exhibited a bimodal pore system of approximately 2.5 and 12 nm, and their structural and chemical properties could be regulated by adjusting the template dosage. At room temperature, using water as the sole oxidant, the optimized Au_0.1Pd_0.05/HTS-21 catalyst achieved a CH₃OH yield of 157.8 mmol g_AuPd^-1·h^-1 with 100% selectivity, substantially outperforming its microporous counterpart. Structural characterization and photoluminescence analysis showed that the mesoporous structure increased the specific surface area and active-site exposure, promoted photogenerated charge separation, and improved molecular diffusion. In situ electron paramagnetic resonance further confirmed that mesopores facilitated the formation of ·CH₃ and ·OH radicals. This work provides a simple route for preparing AuPd-containing hierarchical TS-1 catalysts with promising potential for selective CH₄-to-CH₃OH conversion.

Key words: methane to methanol, selective oxidation, hierarchical TS-1, AuPd alloy nanoparticles, one-step synthesis