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 [Cu-3(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.