High Pressure Synthesis and Characterization of Nanoconfined Polymeric Carbon Monoxide

Studies on pressure-induced polymerization of carbon monoxide are motivated by the desire to understand the chemistry and reactivity of this simple prototypical molecule, and also in search for new high-energy density materials (HEDM). Recent calculations has shown that polycarbonyl chains in a planar zigzag, all trans conformation are actually more stable than the molecular phase even at zero pressure [1], however only short vicinal polycarbonyl compounds, up to R-(CO)5-R have been synthesized by chemists so far [2]. On the other hand, the extended material obtained by compressing bulk CO consists of a mixture of various products, mostly anhydrides [3]. To verify how the strong confinement can alter the reactivity of carbon monoxide under pressure and the structure of the polymer, we have undertaken for the first time pressure-induced polymerization of CO inside the pores of the silicalite, encouraged by earlier syntheses of polymer/silicalite nanocomposites [4, 5]. We identified the new species by observation of the new C=O stretching band in the FTIR spectra, which was absent for the bulk poly-CO extended phase. The single crystal XRD investigation of the recovered sample revealed residual electron density along the channels, as clearly evidenced on Fourier difference maps. Although the polymer chains are orientationally and translationally disordered, the product is chemically less diverse than the polymers obtained by pressure-induced reaction of bulk CO. K. Dziubek gratefully acknowledges the Polish Ministry of Science and Higher Education for financial support through the "Mobilno?? Plus" program. [1] J. Sun, D. D. Klug , C. J. Pickard, R. J. Needs, Controlling the Bonding and Band Gaps of Solid Carbon Monoxide with Pressure, Phys. Rev. Lett. 106, 145502 (2011). [2] M. B. Rubin, R. Gleiter, The Chemistry of Vicinal Polycarbonyl Compounds, Chem. Rev. 100, 1121-1164 (2000). [3] M. Ceppatelli, A. Serdyukov, R. Bini, H. J. Jodl, Pressure Induced Reactivity of Solid CO by FTIR Studies, J. Phys. Chem. B 113, 6652-6660 (2009). [4] M. Santoro, F. A. Gorelli, R. Bini, J. Haines, and A. van der Lee, High-pressure synthesis of a polyethylene/zeolite nano-composite material, Nature Communications 4, 1557 (2013). DOI: 10.1038/ncomms2564. [5] D. Scelta, M. Ceppatelli, M. Santoro, R. Bini, F. A. Gorelli, A. Perucchi, M. Mezouar, A. Van der Lee, J. Haines, Chem. Mater. 26, 2249-2255 (2014). Keywords: high-pressure synthesis, organic-inorganic hybrid materials, nanocomposites, high-energy density materials.