Carbon dioxide and epoxide copolymerization is an industrially relevant means to valorize waste and improve sustainability in polymer manufacturing. Given the value of the polymer products—polycarbonates or polyether carbonates—it could provide an economic stimulus to capture and storage technologies. The process efficiency depends upon the catalyst, and previously Zn(ii)Mg(ii) heterodinuclear catalysts showed good performances at low carbon dioxide pressures, attributed to synergic interactions between the metals. Now, a Mg(ii)Co(ii) catalyst is reported that exhibits significantly better activity (turnover frequency > 12,000 h−1) and high selectivity (>99% CO2 utilization and polycarbonate selectivity) for carbon dioxide and cyclohexene oxide copolymerization. Detailed kinetic investigations show a second-order rate law, independent of CO2 pressure from 1–40 bar, to produce polyols. Kinetic data also reveal that synergy arises from differentiated roles for the metals in the mechanism: epoxide coordination occurs at Mg(ii), with reduced transition state entropy, while the Co(ii) centre accelerates carbonate attack by lowering the transition state enthalpy. This rare insight into intermetallic synergy rationalizes the outstanding catalytic performance and provides a new feature to exploit in other homogeneous catalyses.
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Artz, J. et al. Sustainable conversion of carbon dioxide: an integrated review of catalysis and life cycle assessment. Chem. Rev. 118, 434–504 (2018).
Zhang, X. Y., Fevre, M., Jones, G. O. & Waymouth, R. M. Catalysis as an enabling science for sustainable polymers. Chem. Rev. 118, 839–885 (2018).
Kleij, A. W., North, M. & Urakawa, A. CO2 catalysis. ChemSusChem 10, 1036–1038 (2017).
Zhu, Y., Romain, C. & Williams, C. K. Sustainable polymers from renewable resources. Nature 540, 354–362 (2016).
Wang, Y. Y. & Darensbourg, D. J. Carbon dioxide-based functional polycarbonates: metal catalyzed copolymerization of CO2 and epoxides. Coord. Chem. Rev. 372, 85–100 (2018).
Kozak, C. M., Ambrose, K. & Anderson, T. S. Copolymerization of carbon dioxide and epoxides by metal coordination complexes. Coord. Chem. Rev. 376, 565–587 (2018).
Garden, J. A. Exploiting multimetallic catalysts to access polymer materials from CO2. Green Mater. 5, 103–108 (2017).
Trott, G., Saini, P. K. & Williams, C. K. Catalysts for CO2/epoxide ring-opening copolymerization. Phil. Trans. R. Soc. A 374, 20150085 (2016).
von der Assen, N. & Bardow, A. Life cycle assessment of polyols for polyurethane production using CO2 as feedstock: insights from an industrial case study. Green Chem. 16, 3272–3280 (2014).
Chapman, A. M., Keyworth, C., Kember, M. R., Lennox, A. J. J. & Williams, C. K. Adding value to power station captured CO2: tolerant Zn and Mg homogeneous catalysts for polycarbonate polyol production. ACS Catal. 5, 1581–1588 (2015).
Scharfenberg, M., Hilf, J. & Frey, H. Functional polycarbonates from carbon dioxide and tailored epoxide monomers: degradable materials and their application potential. Adv. Funct. Mater. 28, 1704302 (2018).
Stoesser, T. et al. Bio-derived polymers for coating applications: comparing poly(limonene carbonate) and poly(cyclohexadiene carbonate). Polym. Chem. 8, 6099–6105 (2017).
Subhani, M. A., Kohler, B., Gurtler, C., Leitner, W. & Muller, T. E. Transparent films from CO2-based polyunsaturated poly(ether carbonate)s: a novel synthesis strategy and fast curing. Angew. Chem. Int. Ed. 55, 5591–5596 (2016).
Li, C., Sablong, R. J. & Koning, C. E. Chemoselective alternating copolymerization of limonene dioxide and carbon dioxide: a new highly functional aliphatic epoxy polycarbonate. Angew. Chem. Int. Ed. 55, 11572–11576 (2016).
Luinstra, G. A. Poly(propylene carbonate), old copolymers of propylene oxide and carbon dioxide with new interests: catalysis and material properties. Polym. Rev. 48, 192–219 (2008).
Hauenstein, O., Reiter, M., Agarwal, S., Rieger, B. & Greiner, A. Bio-based polycarbonate from limonene oxide and CO2 with high molecular weight, excellent thermal resistance, hardness and transparency. Green Chem. 18, 760–770 (2016).
Hauenstein, O., Agarwal, S. & Greiner, A. Bio-based polycarbonate as synthetic toolbox. Nat. Commun. 7, 11862 (2016).
Romain, C., Thevenon, A., Saini, P. K. & Williams, C. K. in Carbon Dioxide and Organometallics Vol. 53 (ed. Lu, X. B.) 101–141 (Springer International Publishing, 2016).
Kremer, A. B. & Mehrkhodavandi, P. Dinuclear catalysts for the ring opening polymerization of lactide. Coord. Chem. Rev. 380, 35–57 (2019).
Wang, P. K. et al. Breaking scaling relations to achieve low-temperature ammonia synthesis through LiH-mediated nitrogen transfer and hydrogenation. Nat. Chem. 9, 64–70 (2017).
Kattel, S., Ramirez, P. J., Chen, J. G., Rodriguez, J. A. & Liu, P. Active sites for CO2 hydrogenation to methanol on Cu/ZnO catalysts. Science 355, 1296–1299 (2017).
Chen, Y. Z. et al. Multifunctional PdAg@MIL-101 for one-pot cascade reactions: combination of host-guest cooperation and bimetallic synergy in catalysis. ACS Catal. 5, 2062–2069 (2015).
Powers, D. C. & Ritter, T. Bimetallic redox synergy in oxidative palladium catalysis. Acc. Chem. Res. 45, 840–850 (2012).
Garden, J. A., Saini, P. K. & Williams, C. K. Greater than the sum of its parts: a heterodinuclear polymerization catalyst. J. Am. Chem. Soc. 137, 15078–15081 (2015).
Deacy, A. C., Durr, C. B., Garden, J. A., White, A. J. P. & Williams, C. K. Groups 1, 2 and Zn(II) heterodinuclear catalysts for epoxide/CO2 ring-opening copolymerization. Inorg. Chem. 57, 15575–15583 (2018).
Deacy, A. C., Durr, C. B. & Williams, C. K. Heterodinuclear complexes featuring Zn(ii) and M = Al(iii), Ga(iii) or In(iii) for cyclohexene oxide and CO2 copolymerisation. Dalton Trans. 49, 223–231 (2020).
Kember, M. R., Jutz, F., Buchard, A., White, A. J. P. & Williams, C. K. Di-cobalt(ii) catalysts for the copolymerisation of CO2 and cyclohexene oxide: support for a dinuclear mechanism? Chem. Sci. 3, 1245–1255 (2012).
Kember, M. R., White, A. J. P. & Williams, C. K. Highly active di- and trimetallic cobalt catalysts for the copolymerization of CHO and CO2 at atmospheric pressure. Macromolecules 43, 2291–2298 (2010).
Darensbourg, D. J. & Moncada, A. I. (Salen)Co(II)/n-Bu4NX catalysts for the coupling of CO2 and oxetane: selectivity for cyclic carbonate formation in the production of poly-(trimethylene carbonate). Macromolecules 42, 4063–4070 (2009).
Darensbourg, D. J. Making plastics from carbon dioxide: salen metal complexes as catalysts for the production of polycarbonates from epoxides and CO2. Chem. Rev. 107, 2388–2410 (2007).
Shen, Y.-M., Duan, W.-L. & Shi, M. Chemical fixation of carbon dioxide catalyzed by binaphthyldiamino Zn, Cu, and Co salen-type complexes. J. Org. Chem. 68, 1559–1562 (2003).
Ohkawara, T., Suzuki, K., Nakano, K., Mori, S. & Nozaki, K. Facile estimation of catalytic activity and selectivities in copolymerization of propylene oxide with carbon dioxide mediated by metal complexes with planar tetradentate ligand. J. Am. Chem. Soc. 136, 10728–10735 (2014).
Liu, Y., Ren, W. M., Zhang, W. P., Zhao, R. R. & Lu, X. B. Crystalline CO2-based polycarbonates prepared from racemic catalyst through intramolecularly interlocked assembly. Nat. Commun. 6, 8594 (2015).
Na, S. J. et al. Elucidation of the structure of a highly active catalytic system for CO2/epoxide copolymerization: a salen-cobaltate complex of an unusual binding mode. Inorg. Chem. 48, 10455–10465 (2009).
Darensbourg, D. J. & Yeung, A. D. A concise review of computational studies of the carbon dioxide–epoxide copolymerization reactions. Polym. Chem. 5, 3949–3962 (2014).
Kember, M. R. & Williams, C. K. Efficient magnesium catalysts for the copolymerization of epoxides and CO2; using water to synthesize polycarbonate polyols. J. Am. Chem. Soc. 134, 15676–15679 (2012).
Mishra, V., Lloret, F. & Mukherjee, R. Coordination versatility of 1,3-bis[3-(2-pyridyl)pyrazol-1-yl]propane: Co(II) and Ni(II) complexes. Inorg. Chim. Acta 359, 4053–4062 (2006).
Du, K., Thorarinsdottir, A. E. & Harris, T. D. Selective binding and quantitation of calcium with a cobalt-based magnetic resonance probe. J. Am. Chem. Soc. 141, 7163–7172 (2019).
Halfen, J. A. et al. Synthetic models of the inactive copper(II)−tyrosinate and active copper(II)−tyrosyl radical forms of galactose and glyoxal oxidases. J. Am. Chem. Soc. 119, 8217–8227 (1997).
Itoh, S. et al. Model complexes for the active form of galactose oxidase. Physicochemical properties of Cu(II)− and Zn(II)−phenoxyl radical complexes. Inorg. Chem. 39, 3708–3711 (2000).
DiCiccio, A. M., Longo, J. M., Rodríguez-Calero, G. G. & Coates, G. W. Development of highly active and regioselective catalysts for the copolymerization of epoxides with cyclic anhydrides: an unanticipated effect of electronic variation. J. Am. Chem. Soc. 138, 7107–7113 (2016).
Trott, G., Garden, J. A. & Williams, C. K. Heterodinuclear zinc and magnesium catalysts for epoxide/CO2 ring opening copolymerizations. Chem. Sci. 10, 4618–4627 (2019).
Thevenon, A. et al. Indium catalysts for low-pressure CO2/epoxide ring-opening copolymerization: evidence for a mononuclear mechanism? J. Am. Chem. Soc. 140, 6893–6903 (2018).
Schutze, M., Dechert, S. & Meyer, F. Highly active and readily accessible proline-based dizinc catalyst for CO2/epoxide copolymerization. Chem. Eur. J. 23, 16472–16475 (2017).
Nagae, H. et al. Lanthanide complexes supported by a trizinc crown ether as catalysts for alternating copolymerization of epoxide and CO2: telomerization controlled by carboxylate anions. Angew. Chem. Int. Ed. 57, 2492–2496 (2018).
Ren, W.-M. et al. Highly active, bifunctional Co(III)-salen catalyst for alternating copolymerization of CO2 with cyclohexene oxide and terpolymerization with aliphatic epoxides. Macromolecules 43, 1396–1402 (2010).
Burés, J. A simple graphical method to determine the order in catalyst. Angew. Chem. Int. Ed. 55, 2028–2031 (2016).
Mang, S., Cooper, A. I., Colclough, M. E., Chauhan, N. & Holmes, A. B. Copolymerization of CO2 and 1,2-cyclohexene oxide using a CO2-soluble chromium porphyrin catalyst. Macromolecules 33, 303–308 (2000).
Buchard, A. et al. Experimental and computational investigation of the mechanism of carbon dioxide/cyclohexene oxide copolymerization using a dizinc catalyst. Macromolecules 45, 6781–6795 (2012).
Jutz, F., Buchard, A., Kember, M. R., Fredrickson, S. B. & Williams, C. K. Mechanistic investigation and reaction kinetics of the low-pressure copolymerization of cyclohexene oxide and carbon dioxide catalyzed by a dizinc complex. J. Am. Chem. Soc. 133, 17395–17405 (2011).
Saini, P. K., Romain, C. & Williams, C. K. Dinuclear metal catalysts: improved performance of heterodinuclear mixed catalysts for CO2–epoxide copolymerization. Chem. Commun. 50, 4164–4167 (2014).
Buchard, A., Kember, M. R., Sandeman, K. G. & Williams, C. K. A bimetallic iron(iii) catalyst for CO2/epoxide coupling. Chem. Commun. 47, 212–214 (2011).
Gui, X., Tang, Z. G. & Fei, W. Y. Solubility of CO2 in alcohols, glycols, ethers, and ketones at high pressures from (288.15 to 318.15) K. J. Chem. Eng. Data 56, 2420–2429 (2011).
Darensbourg, D. J., Wei, S.-H., Yeung, A. D. & Ellis, W. C. An efficient method of depolymerization of poly(cyclopentene carbonate) to its comonomers: cyclopentene oxide and carbon dioxide. Macromolecules 46, 5850–5855 (2013).
Lu, X.-B., Liu, Y. & Zhou, H. Learning nature: recyclable monomers and polymers. Chem. Eur. J. 24, 11255–11266 (2018).
Darensbourg, D. J. & Wang, Y. Y. Terpolymerization of propylene oxide and vinyl oxides with CO2: copolymer cross-linking and surface modification via thiol-ene click chemistry. Polym. Chem. 6, 1768–1776 (2015).
Darensbourg, D. J., Chung, W. C., Arp, C. J., Tsai, F. T. & Kyran, S. J. Copolymerization and cycloaddition products derived from coupling reactions of 1,2-epoxy-4-cyclohexene and carbon dioxide. Postpolymerization functionalization via thiol-ene click reactions. Macromolecules 47, 7347–7353 (2014).
Geschwind, J., Wurm, F. & Frey, H. From CO2-based multifunctional polycarbonates with a controlled number of functional groups to graft polymers. Macromol. Chem. Phys. 214, 892–901 (2013).
Yang, G.-W. & Wu, G.-P. High-efficiency construction of CO2-based healable thermoplastic elastomers via a tandem synthetic strategy. ACS Sust. Chem. Eng. 7, 1372–1380 (2019).
Yi, N., Chen, T. T. D., Unruangsri, J., Zhu, Y. & Williams, C. K. Orthogonal functionalization of alternating polyesters: selective patterning of (AB)n sequences. Chem. Sci. 10, 9974–9980 (2019).
della Monica, F. et al. [OSSO]-type iron(III) complexes for the low-pressure reaction of carbon dioxide with epoxides: catalytic activity, reaction kinetics, and computational study. ACS Catal. 8, 6882–6893 (2018).
Zhang, D., Boopathi, S. K., Hadjichristidis, N., Gnanou, Y. & Feng, X. Metal-free alternating copolymerization of CO2 with epoxides: fulfilling “green” synthesis and activity. J. Am. Chem. Soc. 138, 11117–11120 (2016).
Darensbourg, D. J., Mackiewicz, R. M. & Billodeaux, D. R. Pressure dependence of the carbon dioxide/cyclohexene oxide coupling reaction catalyzed by chromium salen complexes. Optimization of the comonomer-alternating enchainment pathway. Organometallics 24, 144 (2005).
Liu, Y., Ren, W.-M., Liu, J. & Lu, X.-B. Asymmetric copolymerization of CO2 with meso-epoxides mediated by dinuclear cobalt(III) complexes: unprecedented enantioselectivity and activity. Angew. Chem. Int. Ed. 52, 11594–11598 (2013).
Ren, W.-M., Liu, Z.-W., Wen, Y.-Q., Zhang, R. & Lu, X.-B. Mechanistic aspects of the copolymerization of CO2 with epoxides using a thermally stable single-site cobalt(III) catalyst. J. Am. Chem. Soc. 131, 11509–11518 (2009).
Kepp, K. P. A quantitative scale of oxophilicity and thiophilicity. Inorg. Chem. 55, 9461–9470 (2016).
Hill, M. S., Liptrot, D. J. & Weetman, C. Alkaline earths as main group reagents in molecular catalysis. Chem. Soc. Rev. 45, 972–988 (2016).
Reiter, M., Vagin, S., Kronast, A., Jandl, C. & Rieger, B. A Lewis acid [small beta]-diiminato-zinc-complex as all-rounder for co- and terpolymerisation of various epoxides with carbon dioxide. Chem. Sci. 8, 1876–1882 (2017).
Liu, Y., Ren, W.-M., He, K.-K. & Lu, X.-B. Crystalline-gradient polycarbonates prepared from enantioselective terpolymerization of meso-epoxides with CO2. Nat. Commun. 5, 5687–5694 (2014).
Nakano, K., Hashimoto, S. & Nozaki, K. Bimetallic mechanism operating in the copolymerization of propylene oxide with carbon dioxide catalyzed by cobalt–salen complexes. Chem. Sci. 1, 369–373 (2010).
Ouyang, T. et al. Dinuclear metal synergistic catalysis boosts photochemical CO2-to-CO conversion. Angew. Chem. Int. Ed. 57, 16480–16485 (2018).
Ouyang, T., Huang, H. H., Wang, J. W., Zhong, D. C. & Lu, T. B. A dinuclear cobalt cryptate as a homogeneous photocatalyst for highly selective and efficient visible-light driven CO2 reduction to CO in CH3CN/H2O solution. Angew. Chem. Int. Ed. 56, 738–743 (2017).
Hogue, R. W., Schott, O., Hanan, G. S. & Brooker, S. A smorgasbord of 17 cobalt complexes active for photocatalytic hydrogen evolution. Chem. Eur. J. 24, 9820–9832 (2018).
Romain, C. et al. Chemoselective polymerizations from mixtures of epoxide, lactone, anhydride, and carbon dioxide. J. Am. Chem. Soc. 138, 4120–4131 (2016).
Chen, T. T. D., Zhu, Y. & Williams, C. K. Pentablock copolymer from tetracomponent monomer mixture using a switchable dizinc catalyst. Macromolecules 51, 5346–5351 (2018).
Stößer, T. & Williams, C. K. Selective polymerization catalysis from monomer mixtures: using a commercial Cr‐salen catalyst to access ABA block polyesters. Angew. Chem. Int. Ed. 57, 6337–6341 (2018).
Stößer, T., Mulryan, D. & Williams, C. K. Switch catalysis to deliver multi-block polyesters from mixtures of propene oxide, lactide, and phthalic anhydride. Angew. Chem. Int. Ed. 57, 16893–16897 (2018).
Stößer, T., Chen, T. T. D., Zhu, Y. & Williams, C. K. ‘Switch’ catalysis: from monomer mixtures to sequence-controlled block copolymers. Phil. Trans. R. Soc. A 376, 20170066 (2018).
Siedschlag, R. B. et al. Catalytic silylation of dinitrogen with a dicobalt complex. J. Am. Chem. Soc. 137, 4638–4641 (2015).
Wu, B., Gramigna, K. M., Bezpalko, M. W., Foxman, B. M. & Thomas, C. M. Heterobimetallic Ti/Co complexes that promote catalytic N–N bond cleavage. Inorg. Chem. 54, 10909–10917 (2015).
Dugan, T. R., MacLeod, K. C., Brennessel, W. W. & Holland, P. L. Cobalt–magnesium and iron–magnesium complexes with weakened dinitrogen bridges. Eur. J. Inorg. Chem. 2013, 3891–3897 (2013).
Li, J. et al. Cobalt-catalyzed electrophilic aminations with anthranils: an expedient route to condensed quinolines. J. Am. Chem. Soc. 141, 98–103 (2019).
Mei, R., Sauermann, N., Oliveira, J. C. A. & Ackermann, L. Electroremovable traceless hydrazides for cobalt-catalyzed electro-oxidative C–H/N–H activation with internal alkynes. J. Am. Chem. Soc. 140, 7913–7921 (2018).
Bakewell, C., Ward, B. J., White, A. J. P. & Crimmin, M. R. A combined experimental and computational study on the reaction of fluoroarenes with Mg–Mg, Mg–Zn, Mg–Al and Al–Zn bonds. Chem. Sci. 9, 2348–2356 (2018).
We acknowledge the EPSRC (EP/L017393/1, EP/S018603/1, EP/K014668/1) and EIT Climate KIC (EnCO2re) for research funding. A.C.D. acknowledges an EPSRC CASE award, with Econic Technologies, for financial support. A.F.R.K. acknowledges the support of Wadham College, Oxford for an RJP Williams Junior Research Fellowship. A.R. acknowledges Imperial College London for a Junior Research Fellowship (JRF).
C.K.W. is a director of Econic Technologies.
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Deacy, A.C., Kilpatrick, A.F.R., Regoutz, A. et al. Understanding metal synergy in heterodinuclear catalysts for the copolymerization of CO2 and epoxides. Nat. Chem. 12, 372–380 (2020). https://doi.org/10.1038/s41557-020-0450-3
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