Preparation And Properties Of CO₂ Separation Membrane Based On Polymer Of Intrinsic Microporosity

In order to improve the global climate and environment,capture and storage of CO₂ has received increasing attention.Compared with traditional separation methods,membrane separation technology has shown unique advantages in the field of gas separation due to its low energy consumption and simple operation.Polymers of Intrinsic Microporosity?PIMs?have excellent thermal stability and high gas permeability.In this paper,the simplest PIM-1 was used as the polymer matrix,polydopamine-derived sub-microspheres?PDASS?and amorphous metal organic framework?aMOF?were selected as fillers to prepare two mixed matrix membranes for CO₂/N₂ separation,respectively.The specific research contents and conclusions are as follows:?1?The PDASS was prepared by oxidative self-polymerization of dopamine under low alkaline conditions.The characterization results showed that the size of PDASS became larger and the BET surface area decreased with the increase of reaction time.PDASS with a reaction time of 5 h was chosen as filler to prepare the PIM-1/PDASS mixed matrix membrane.The characterization of the membranes proved that the addition of PDASS caused the polymer chain rearrangement,which improved compatibility between PIM-1 and PDASS.In addition,the PDASS occupied the effective channel for gas transport of membranes,and the amine,imine groups increased the solubility coefficient of CO₂.Finally,the permeability of PIM-1/PDASS membrane for CO₂ and N₂ decreased,but the ideal selectivity is obviously improved.When the loading of PDASS is 25 wt%,the ideal selectivity of PIM-1/PDASS reached 35,which offer 1.6-fold enhancement compared with the pure PIM-1 film,exceeding the Robeson upper bound.Importantly,the test of physical aging behavior of permeability showed that the combination of PIM-1 and PDASS can effectively delay the aging of the film.?2?The aMOF was synthesized in water solvent.The characterization results showed that aMOF had no characteristics of crystalline MOF.Then it was used as filler to prepare PIM-1/aMOF mixed matrix membrane.The characterization of the membranes proved that aMOF could be uniformly dispersed in PIM-1 and has good interfacial compatibility with PIM-1,due to its amorphous structure and the noncovalent effect between a large amount of free SiF₄ in aMOF with PIM-1.The addition of aMOF significantly improved the permeability of CO₂,and at the same time the ideal selectivity of CO₂/N₂ was improved to some extent.Especially,when the loading of aMOF is 5%,the CO₂ permeability of PIM-1/aMOF was 6268.1 Barrer,which increased by 51.7%compared with the pure PIM-1 film,while maintaining the ideal selectivity of 26.3,exceeding the Robeson upper bound.More importantly,this study uses amorphous MOF for gas separation membranes and provides a new research direction to solve the problem of interface compatibility.