Zeolite Imidazole Framework-based Mixed Matrix Membrane For Gas Separation Study

Membrane-based gas separation technology has a great of advantage,such as low energy-consumption,sustainable operation,small footprint,etc.,which is an ideal next-generation separation technology.At present,the commercial application of gas separation membranes are mainly polymer membranes because of the production cost of polymer membranes is lower and easy to process.The gas transport mechanism of polymer membranes mainly depends on the dissolution-diffusion and suffer from a well-known trade-off effect?the mutual constraint between permeability and selectivity?.Although inorganic membranes?such as metal organic framework?MOF?membranes,zeolite imidazole framework?ZIF?membranes,etc.?exhibit a high permeability and selectivity,inorganic membranes are brittle.Mixed-matrix membrane can effectively combine the high selectivity of the inorganic filler and the easy processing and continuity of the polymer membrane.The selection and preparation of the inorganic filler in the mixed-matrix membrane is the key to achieve high permeability and high selectivity of the mixed-matrix membrane.In this paper,the development of high-performance mixed-matrix membranes is the goal.ZIF-8?Zn?Hmim?₂,Hmim=2-methylimidazole?is used as the structure control object.The mixed matrix membranes were fabricated via incorporating the functional ZIF-8 into polymer matrix and the obtained membranes separation performance was studied.The main research contents of the paper are as follows:?1?The amino-functionalized heterometallic ZIF-8?NH₂-Co/ZIF-8?was fabricated by doping isometallic cobalt and partial substitution of 2-methylimidazole with 2-aminobenzimidazole ligand.The adsorption capacity of NH₂-Co/ZIF-8 for CO₂ has been improved.The NH₂-Co/ZIF-8 as inorganic filler was incorporated into a CO₂ affinity material polyethylene oxide?PEO?to fabricate a high permeability and selective mixed-matrix membrane via UV-grafting.The ester groups in the methacrylate-terminated PEO and acrylate-terminated PEO chelate the metal ions in NH₂-Co/ZIF-8,resulting in NH₂-Co/ZIF-8 homogenous dispersed in the polymer.The solubility coefficient of CO₂ in the NH₂-Co/ZIF-8 PEO mixed matrix membrane has been improved,which effectively improving the CO₂ permeability and CO₂/N₂selectivity.The separation performance of the obtained mixed matrix membrane showed a CO₂ permeability of 2916.0 barrer and a CO₂/N₂ selectivity of 47.0,surpassing the 2008 Robeson's upper bound.?2?The 2-aminoimidazole in situ substitution of 2-methylimidazole in the ZIF-8framework and the NH₂-ZIF-8?X?powder is synthesized.The-NH₂ group on di-aminoimidazole can effectively enhance the affinity of ZIF-8 for CO₂.The obtained NH₂-ZIF-8?X?powder was dispersed in a glassy rigid polyimide polymer to prepare a mixed matrix membrane.The CO₂ permeability of the 20%NH₂-ZIF-8?50?/6FDA-DAM hybrid membrane increased from 504.8 barrer to 1258.8barrer and the selectivity of CO₂/CH₄ increased from 21.3 to 35.1.The separation performance of obtained hybrid membrane has surpassed the 2008 Robeson's upper bound and not limited via the Trade-off effects.The NH₂-ZIF-8/6FDA-DAM hybrid membrane exhibits an industrial application for natural gas purification.