Mechanochemical Synthesis of High-Entropy MOF-74 with Multiple Active Sites for CO2 Adsorption and Synergistic Conversion

Compared with monometallic metal–organic frameworks (MOFs), the synergistic effect of multiple metals significantly enhances the catalytic performance of the CO2 cycloesterification reaction, leading to improved CO2 adsorption and catalytic conversion capabilities. To investigate this concept, a high-entropy MOF-74 (HE-MOF-74) with a uniform distribution of five distinct metal ions (Zn2+, Mg2+, Ni2+, Co2+, and Cu2+) was successfully synthesized using a straightforward mechanical ball milling technique and comprehensively characterized (including structural, morphological, and physicochemical properties). The results reveal that HE-MOF-74 exhibits significantly increased specific surface area and CO2 adsorption capacity compared with those of monometallic MOF-74. The presence of multiple unsaturated metal centers as Lewis acid sites, oxygen atoms linking the metals, and ligand-based hydroxyl groups serving as base sites enable efficient immobilization of CO2 into cyclic carbonate. This study introduces a novel synthetic approach for the green and efficient production of HE-MOF-74 and proposes a new application for CO2 utilization.