Probing the structure of porous liquids with neutron scattering experiment and molecular simulation

BORIONI, JOSÉ L.; DEL PÓPOLO, MARIO G.; KOHANOFF, JORGE ; JAMES, STUART

Diblin

Congreso; Marie Curie Computer Simulation of Chemical Technologies involving Confined Liquids,; 2018

University College Dublin

The prospect of engineering permanent porosity into the liquid state is of fundamental interest and potentially, in the longer term, may lead to novel separation and storage technologies, and customised reaction media. In liquids, porosity is predominantly limited to small vacancies which are generated transiently between the molecules as they move. As demonstrated recently, however, liquids bearing permanent cavities can be produced by dissolving hollow cage-like molecules into solvents which are too large to enter the intramolecular cavity. We refer to these mixtures as ?Porous Liquids? (PLs). One of the most interesting features of PLs is that they can dissolve gases and small guest molecules in a size selective manner. In the present work we apply total neutron scattering and Molecular Dynamics simulations toinvestigate the molecular structure and mesoscopic ordering of a prototypical PL. The liquidconsists of rigid iminospherand cages dispersed in perchloropropene at a molar ratio of 1:36. Static structure factors, S(Q)s, are computed for the pure solvent and the PL loaded with hydrogenated (CHCl3) and deuterated (CDCl3) chloroform, and compared to experimental diffraction profiles. We assign the most prominent features of the S(Q)s to specific solvent-solvent and solvent-cage contacts. More importantly, we show that the presence of a single CDCl3 molecule inside each cage is enough to significantly alter the contrast in the diffraction profiles of the PL at low Q. Our results indicate that adding controlled amounts of small deuterated guests to a PL can be used to probe by neutron scattering both its intrinsic porosity and mesoscale order.