We recently developed a new non-equilibrium molecular dynamics simulation method  in order to simulate the permeation of pure fluids and mixtures through membranes, namely "Concentration Gradient Driven Molecular Dynamics" (CGD-MD). This new 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 maintain a concentration gradient and drive the diffusion of the molecules through the membrane. This is aimed at mimicking membrane separation experiments; for instance, high concentration/pressure at the feed side and vacuum at the permeate side. CGD-MD addresses two main shortcomings of previous non-equilibrium MD methods used for simulating membrane separation processes at the molecular scale. First, it avoids the feed depletion issue and allows running steady state and continuous simulations for unrestricted simulation times. Second, it maintains the feed composition at a target value without the need of any complex Monte Carlo-MD coupling. We demonstrate the new method for the separation of various gas mixtures in a MOF membrane as well as a composite MOF/Polymer mebrane.
 Ozcan, A., Perego, C., Salvalaglio, M., Parrinello, M., Yazaydin, O.*; "Concentration gradient driven molecular dynamics: a new method for simulations of membrane permeation and separation", Chemical Science, 2017, 8, 3858–3865.