Described for the first time is that carbon dioxide (CO2) can be successfully inserted into aryl C−H bonds of the backbone of a metal–organic framework (MOF) to generate free carboxylate groups, which serve as Brønsted acid sites for efficiently catalyzing the methanolysis of epoxides. The work delineates the very first example of utilizing CO2 for heterogeneous C−H activation and carboxylation reactions on MOFs, and opens a new avenue for CO2 chemical transformations under mild reaction conditions. Framed: CO2 is utilized for heterogeneous C−H activation and carboxylation reactions on metal–organic frameworks (MOFs). The formed carboxylate groups serve as Brønsted acid sites and were shown to efficiently catalyze the methanolysis of epoxides. This work introduces a new avenue for CO2 chemical transformations under mild reaction conditions.