High Pressure Physics and Chemistry in confined systems (C-based Molecules)

I will present on the discovery of several compounds and composite materials obtained through the recent year, by reacting simple carbon bearing molecules, at high pressures, in the sub-nanopores of two non catalytic, pure SiO2 zeolites: silicalite and ZSM-22. I will first show two different CO2-SiO2 compounds. One of these is a disordered silicon carbonate, with carbon in threefold coordination by oxygen1. This phase was obtained by reacting a mixture of silicalite and nano-confined CO2 at 18-26 GPa and 600-980 K. The transformation is reversible upon reducing pressure. More recently, a crystalline CO2-SiO2 solid solution was obtained by reacting the same type of initial mixture, CO2/SiO2, to temperatures in excess of 4000 K, at about 20 GPa2. The material was identified as an ?-cristobalite like phase (P41212) with stoichiometric formula: C0.7SiO0.3O2. Remarkably, the novel compound was recovered at ambient conditions. I will then report on the high pressure (GPa) polymerization of ethylene, acetylene and CO in the nanochannels of the zeolites, leading to the formation of novel nanocomposite materials, which are recovered to ambient P and have remarkable properties. A polyethyelene/silicalite composite, PESIL, was formed with tunable thermo-mechanical properties and potential null thermal expansion3. Then we obtained a conjugated chain/silicalite composite, PASIL, where branched, semiconducting oligomers are buried in the host, protecting zeolite4. Very recently, we also obtained the formation of 1D conducting polymers, true polyacetylene (PA) in this case, in the 1D host channels of ZSM-22. In this composite the electronic density of state of PA is expected to exhibit van Hove singularities related to quantum 1D confinement, which could lead to future technological applications. I will finally show the polymerization of CO in both silicalite and ZSM22, which leads to more stoichiometrically and structurally ordered polymers than obtained so far in the bulk, high pressure polymerization of this simple system. The polyCO/zeolite composites could constitute a class of interesting energetic materials. Investigations were based on resistively and laser heated diamond anvil cells, and in situ IR and Raman spectroscopy, and single crystal and powder X-ray diffraction, performed by either laboratory sources or synchrotron radiation. References [1] M. Santoro, F. Gorelli, J. Haines, O. Cambon, C. Levelut, and G. Garbarino, Proc. Natl. Acad. Sci. U. S. A. 108, 7689 (2011). [2] M. Santoro, F. A. Gorelli, R. Bini, A. Salamat, G. Garbarino, C. Levelut, O. Cambon, J. Haines, Nature Communications 5, 3761 (2014). DOI: 10.1038/ncomms4761. [3] M. Santoro, F. A. Gorelli, R. Bini, J. Haines, and A. van der Lee, Nature Communications 4, 1557 (2013). DOI: 10.1038/ncomms2564. [4] D. Scelta, M. Ceppatelli, M. Santoro, R. Bini, F. A. Gorelli, A. Perucchi, M. Mezouar, A. van der Lee, and J. Haines, Chem. Mater. 26, 2249-2255 (2014).