Sequestering CO<sub>2</sub> 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 CO<sub>2</sub> and oxiranes provides a viable industrial process for the production of these important chemicals. In this study, we have demonstrated that CO<sub>2</sub> collected under aerobic conditions at atmospheric pressure over [Cu<sub>3</sub>(btc)<sub>2</sub>(H<sub>2</sub>O)<sub>3</sub>] (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 CO<sub>2</sub> catalyzed by Co­(III) salen catalysts at optimal pressure. That is, CO<sub>2</sub> 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 <i>cis</i>-2-butylene oxide monomer with CO<sub>2</sub>. Comparative studies using CO<sub>2</sub> 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 CO<sub>2</sub> captured from point sources for the synthesis of useful chemicals without requiring mechanical compression.