A new porous metal-metalloporphyrin framework, MMPF-10, has been constructed from an octatopic porphyrin ligand, which links copper paddlewheel units to form a framework with fmj topology. In situ metallation of the porphyrin ligands provides MMPF-10 with two unique accessible Cu(ii) centers. This allows it to behave as an efficient Lewis acid catalyst in the first reported reaction of CO2 with aziridines to synthesize oxazolidinones catalyzed by an MMPF.