Zirconium metal-organic cage decorated with squaramides imparts dual activation for chemical fixation of CO 2 under mild conditions.

A "two-in-one" dual activation strategy has been developed to give high-density hydrogen-bonding (HB) active units and Lewis acid (LA) active centres by immobilizing squaramides into metal-organic cages (MOCs). The obtained MOC served as an efficient catalyst for the chemical fixation of CO 2 under mild conditions up to 99% yields with good recyclability, and the mechanism of high catalytic activity has been further explored.