Preparation of polymer membrane with intrinsic microporosity modified by ZIF-8 and its separation performance for CO2
In order to improve the CO2 separation of intrinsic microporosity(PIMs)membrane of polymers,thePIM-1 membr-ane was functionally modified.First,the PIM-1 membrane was introduced Zn2+was introduced into the PIM-1 membrane by alkaline hydrolysis and replacement,and then the modified PIM-1 membrane was immersed in a methanol solution of 2-methylimidazole to grow zeolitic imidazolate framework-8(ZIF-8)selective layer on the membrane surface at room temperature.The defect-free ZIF-8 modified PIM-1 membrane(pZIF-8@PIM-1)was obtained after silicone rubber filling.The performance and structure were tested and characterized.The re-sults showed that the ZIF-8 selective layer with a thickness of about 0.8 μm was successfully grown on the sur-face of the ion-modified PIM-1 membrane,and the crystal size was uniform with a particle size of about 200 nm.Compared with the PIM-1 membrane,the CO2 diffusion coefficient of pZIF-8@PIM-1 decreased significantly and the CO2/N2 diffusivity selectivity increased from 0.89 to 1.01 due to the cross-linking of multivalent metal ions and the presence of ZIF-8 selective layer.The Lewis acid-base interaction between the nitrogen-containing organic heterocyclic ring of ZIF-8 and CO2 and the affinity of the electrostatic potential on the 2-methylimidazole ring for CO2 led to the increase of the CO2 solubility coefficient of pZIF-8@PIM-1 and the improvement of the CO2/N2 solubility selectivity from 18.56 to 20.31.The dual improvement of CO2/N2 diffusivity selectivity and CO2/N2 solubility selectivity of the modified PIM-1 membrane jointly promoted the improvement of CO2/N2 selectivity from 16.57 to 20.43,with good CO2 separation performance.
gas separation membranepolymers of intrinsic microporosityzeolitic imidazolate framework-8(ZIF-8)CO2 separation
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