Post-modification of PIM-1 and simultaneously in situ synthesis of porous polymer networks into PIM-1 matrix to enhance CO2 separation performance

Post-modification of the chemical structures can be used to tailor the properties of polymers of intrinsic microporosity (PIM-1), which shows promise for application of PIM-1 gas separation membrane. Methane sulfonic acid (MSA) is capable of hydrolyzing and crosslinking nitrile groups of PIM-1 to form carboxylic acid-contained and triazine groups crosslinked PIM-1 (cPIM-1), and simultaneously catalyze in situ synthesis of porous polymer networks (PPNs) in PIM-1 matrix. These reactions were carried out at the same time by a one-step method. Characterization of hydrolysis and crosslinking process of nitrile groups in PIM-1 was performed by ATR, XPS, solubility, and 1H NMR analysis. MSA catalyzed synthetic approach of PPNs includes the trimerization of three acetyl groups and involves a coupled process of polymerization and membrane architecture formation. Finally, the process of crosslinking and hydrolysis can provide enhanced gas pair selectivity of PIM-1 membrane (cPIM-1) while the gas permeability of the membranes (cPIM-1/PPNs) can be increased by the incorporation of PPNs microstructure networks. As a result, the optimal cPIM-1/PPNs showed Roberson's 2008 upper bound separation performance for CO2/CH4 and CO2/N2. The cPIM-1/PPN2-3% membrane demonstrated the best CO2 comprehensive separation performance with the permeability of almost 11511 Barrer, with ideal selectivity of 24.3 and 22.2 for CO2/N2 and CO2/CH4 respectively. Furthermore, the cPIM-1/PPNs membranes show excellent anti-aging properties. This indicates that MSA-catalyzed hydrolysis, crosslinking and in situ synthesis PPNs can effectively adjust the topological structure of PIM-1 membrane for CO2 separation.