Sequestering CO2 for Short-Term Storage in MOFs: Copolymer Synthesis with Oxiranes

It is presently well-established that the synthesis of polycarbonates or cyclic carbonates from metal-catalyzed reactions of CO2 and oxiranes provides a viable industrial process for the production of these important chemicals. In this study, we have demonstrated that CO2 collected under aerobic conditions at atmospheric pressure over [Cu3(btc)2(H2O)3] (btc = benzene-1,3,5-tricarboxylate) or HKUST-1, a commercially available metal–organic framework material (MOF), can be utilized to synthesize poly­(propylene carbonate) from propylene oxide and CO2 catalyzed by Co­(III) salen catalysts at optimal pressure. That is, CO2 thermally released from the MOF material selectively affords copolymer in the pressure range that is not rate-limiting. Similar results were noted for the copolymerization of the much less reactive cis-2-butylene oxide monomer with CO2. Comparative studies using CO2 provided directly from a compressed gas source gave similar results. This investigation provides a baseline study for the practical use of atmospheric pressure or below CO2 captured from point sources for the synthesis of useful chemicals without requiring mechanical compression.