Modulating the microenvironment of AuPd nanoparticles using metal–organic frameworks for selective methane oxidation

Abstract

Direct and selective oxidation of methane (CH₄) into methanol (CH₃OH) under ambient conditions remains a grand challenge because of the high energy barrier of CH₄ activation and the complicated processes involved. Herein, by incorporating AuPd alloy nanoparticles (NPs) into a series of Cu²⁺-doped metal–organic frameworks (MOFs), namely AuPd@Cu-UiO-66_x, efficient and direct catalytic conversion of CH₄ to CH₃OH can be achieved at mild temperature (70 °C) with H₂O₂ as an oxidant. The Cu-UiO-66 serving as the microenvironment parameter not only regulates the electronic state of AuPd NPs to improve the CH₄ adsorption and activation, but also affects the generation of hydroxyl radicals (˙OH) in H₂O₂ reaction pathways, which consequently results in a volcano-type dependency of the CH₃OH selectivity on the Cu contents. This work represents the first finding on achieving direct catalytic oxidation of CH₄ to CH₃OH under mild conditions by modulating the microenvironment of catalytic centers based on a MOF platform.