A Highly Rigid and Conjugated Microporous Polymer Membrane for Solvent Permeation and Biofuel Purification: A Molecular Simulation Study
Jie Liu, Wei Wan, Jianwen Jiang
Abstract
With rigid π-conjugated skeletons and permanent micropores, conjugated microporous polymers (CMPs) have attracted increasing interest. Nevertheless, most current studies for CMPs are largely focused on the adsorption of gases and organic molecules. Herein, a molecular simulation study is reported to investigate a CMP membrane (p-CMP) for solvent permeation and biofuel (represented by ethanol/water mixtures) purification. The permeabilities of four solvents (methanol, ethanol, acetonitrile, and acetone) are predicted and found to match well with available experimental data. Between the permeability and solvent properties (i.e., viscosity and molecular size), a good correlation is established. Due to the hydrophobic nature of p-CMP, the solvent–membrane interaction is largely attributed to the nonpolar group of solvent. For ethanol/water separation, ethanol flux is observed to increase with increasing ethanol composition xe in the mixture, while water flux remains nearly constant. The total flux through p-CMP is about 5 times of that through PIM-1 membrane for ethanol/water mixture at xe = 10 wt %, and the separation factor is 15 times higher. Moreover, the total flux is approximately two orders of magnitude larger than that of MFI membrane at xe = 5 wt %. This simulation study microscopically elucidates the experimentally observed solvent permeation through p-CMP membrane, predicts the performance for biofuel purification, and suggests p-CMP membrane might be useful for high-performance separation.