Ultrasonic-assisted synthesis of Ce-doped high-entropy oxides with enhanced oxygen vacancies from MOF precursors for low-temperature CO oxidation

Ultrasonic-assisted strategy prepares Ce-doped HEOs from high-entropy MOFs. • MOF-derived HEOs retain porous structures and high surface areas after calcination. • Ce doping promotes CO conversion in low-temperature CO oxidation. Developing efficient and durable noble-metal-free catalysts for low-temperature CO oxidation remains a challenge, as conventional transition metal oxides are plagued by sintering, limited active-site accessibility, and poor oxygen activation capability. Herein, a facile and scalable ultrasonic-assisted strategy was developed to synthesize a Ce-doped high-entropy metal–organic framework precursor (6-HE-MOF), followed by controlled calcination to obtain high-entropy oxide (HEO) catalysts. Among them, 6-HEO-550 exhibited the highest catalytic efficacy, achieving complete CO conversion at 140 °C and preserving 100% conversion across a 50 h continuous stability test at 140 °C. Comprehensive structural and surface characterizations reveal that the MOF-derived architecture effectively suppresses particle sintering while preserving an open mesoporous structure with a high specific surface area (60.3 m 2 g −1 ), thereby facilitating active-site exposure and mass transport. Meanwhile, Ce incorporation enriches oxygen vacancies and reactive adsorbed oxygen species. In situ DRIFTS further demonstrates that Ce promotes CO chemisorption and accelerates the formation and conversion of reactive carbonate intermediates, resulting in a reduced apparent activation energy of 51.8 kJ mol −1 . This work demonstrates that coupling high-entropy multicomponent engineering with Ce-induced defect modulation through a MOF-derived strategy provides an effective and scalable route for developing highly efficient, durable, and noble-metal-free catalysts for low-temperature CO oxidation. Download: Download high-res image (77KB) Download: Download full-size image