Preparation And CO₂/N₂ Separation Performance Of Covalent Organic Frameworks/polymer Of Intrinsic Microporosity Mixed Matrix Membranes

Nowdays,the climate and environmental problems are becoming increasingly serious because of the increasing CO₂ concentration in the atmosphere.Carbon dioxide capture is considered to be the key to sustainable development.Among them,membrane separation technology is prmising because of its high efficiency,energy saving and environmental friendliness.Mixed Matrix membranes（MMMs）can effectively combine both the merit of polymer matrix and inorganic filler,and has a bright prospect in gas separation membrane.In this study,to prepare high performance COFs/PIM-1 MMMs,polymer of intrinsic microporosity（PIM-1）was used as the membrane matrix,which has the advantages of high porosity,high gas permeability and solution processing.Covalent organic frameworks（COFs）were used as fillers,which have many advantages such as high specific surface area,high porosity and excellent interfacial compatibility.And the separation performance of the mixed matrix membranes for CO₂/N₂ was studied.The main research contents are as follows:（1）First,PIM-1 with weight average molecular weight（M_w）of 134820 g mol^-1and TPB-DMTP-COF with specific surface area（BET）of 2137.6 m²g^-1 were successfully prepared.Then,using ionic liquid（ILs）with high solubility to CO₂ to prepare composite IL@COF by impregnation method.Then IL@COF was incorporated into PIM-1 to fabricate homogeneous mixed matrix membranes with different mass concentrations.The existence of IL@COF improved the solubility selectivity of CO₂/N₂ in MMMs.The 1 wt%IL@COF/PIM-1 MMMs showed excellent permeability coefficient of CO₂（9130.7 Barrer）and selectivity of CO₂/N₂（20.0）,which overcomed the relationship of Trade-off and surpassed the Robeson upper bound（2008）.（2）In order to further improve the CO₂/N₂ permeability selectivity of COFs/PIM-1 MMMs,TPB-DMTP-COF was modified by polydopamine（PDA）.Mixed matrix membranes with different mass concentrations were prepared by incorporating PDA@COF in PIM-1 and applied to the separation of CO₂/N₂.The primary amine,secondary amine and other functional groups in PDA@COF can not only improve the interfacial compatibility by producing hydrogen bonding with PIM-1,but also increase the dissolution coefficient of CO₂ in the membrane.Compared with pure PIM-1 membrane,the permeability coefficient of CO₂ and the ideal selectivity of CO₂/N₂ of 3 wt%PDA@COF/PIM-1 MMMs was 9750.6 Barrer and 26.4,which overcomed the relationship of Trade-off and surpassed the Robeson upper bound（2008）.At the same time,this mixed matrix membrane maintained stable performance during pressure test of 1-5 bar and long time test of 120 h,respectively.