SESSION 4: TOWARDS LONGER LENGTH SCALES

Direct Simulation of Gas Transport and Separations in Composite MOF/Polymer Membranes at the Molecular Scale

Department of Chemical Engineering, University College London, London, WC1E 7JE, United Kingdom

Mixed-matrix membranes (MMMs) are comprised of a continuous polymeric phase in which a carefully selected inorganic material is dispersed, changing the properties of the composite membrane, ideally to give higher permeability of the desirable gas species, and often simultaneously improving mechanical properties. In particular, MMMs which incorporate polymers and MOFs have been hailed for a wide range of membrane-based liquid and gas separation processes.^[1-2] As such, fundamental understanding of the polymer/MOF interface/structure and of the fluid transport, whether in gas or liquid phase, through the composites is crucial to the rational selection of MOF/polymer pairs to achieve outstanding separation of mixtures. We recently developed a non-equilibrium molecular dynamics simulation method^[3] in order to study thepermeation of pure fluids and separation of mixtures in membranes, namely "Concentration Gradient Driven Molecular Dynamics" (CGD-MD). This method works by employing bias forces to fix the concentration of fluids (pure or mixture) at the inlet and outlet of a membrane in order to create and maintain a concentration gradient across the membrane which drives the diffusion of molecules. This is aimed at providing a realistic representation of membrane separation experiments; for instance, high concentration/pressure at the feed side and vacuum at the permeate side. In this talk I’ll present our research on the application of the CGD-MD method to study gas transport and separation in MOF and composite MOF/Polymer membranes.

[1] B. Zornoza, C. Telleza, J. Coronasa, J. Gascon and F. Kapteijn, Metal organic framework based mixed matrix membranes: An increasingly important field of research with a large application potential, Micropor. Mesopor. Mater., 166, 67-68, 2013
[2] R. Semino, N. A. Ramsahye, A . Ghoufi and G. Maurin, Microscopic Model of the Metal−OrganicFramework/Polymer Interface: A First Step toward Understanding the Compatibility in Mixed Matrix Membranes, ACS Appl. Mater. Interfaces, 8, 809−819, 2016
[3] A. Ozcan, C. Perego, M. Salvalaglio, M. Parrinello, and O. Yazaydin, Concentration gradient driven molecular dynamics: a new method for simulations of membrane permeation and separation, Chem. Sci., 8, 3858-3865, 2017