Enhancing CO2 cycloaddition through ligand functionalization: A case study of UiO-66 metal-organic frameworks

• Utilizing isoreticular UZr-X to transfer CO 2 into cyclic carbonates. • Enhancing CO 2 cycloaddition by synergistic effects between Lewis acid/base sites. • For UZr-NH 2 , –NH 2 /Zr 4+ acts as base/acid sites, and led to the highest activity. • "Adsorption–coordination–activation" mechanism is proposed through DRFTIR and DFT.