New Synthetic Routes And Separation Performance Of MOF Membrane

Membrane separation technology can address issues related to global climate change and energy security.Metal-organic frameworks?MOF?with uniform pore size and good adsorption ability of gases is a kind of promising materials for membrane separation.In the last two decades,we have witnesses the fast growth of MOF membrane,including different synthesis methods and the architectural design from microscopic and mesoscopic levels.However,MOF membrane is facing with challenges for further practical application in industry,the high cost and high equipment requirements during the solvothermal synthesis process.Simpler,cheaper,and high-yield synthesis methods are expected to lead to the preparation of MOF membranes on the large scale.Herein,we focused on some MOF membranes,optimized synthesis methods and proposed a green,safe and synthetic route for large-scale production.The research contents of this paper are as followed:?1?A versatile solvent-free strategy is demonstrated to fabricate MOF membranes on different substances with the advantages of environmental protection and good for large-scale production.Three different MOF membranes are prepared in this work,ZIF-8,ZIF-9,and ZIF-67.According to the targeted MOF species,one specific metal precursor film is deposited on the support by electrochemical method,which is very facile and environmentally friendly.Then,the ligand powders are coated on the top and pressed deeply,which is followed by heating up to some temperature for a certain period.The gas permeances through all the three MOF membranes are measured by Wicke-Kallenbach technique.All of the membranes show ideal selectivity larger than Knudsen values for several gas pairs.It is noteworthy that the H₂/CO₂ separation selectivity of ZIF-8 membrane here is significantly higher than other ZIF-8membranes reported elsewhere.This is an effective evidence that the solvent-free method to fabricating MOF membranes can make sense.Moreover,it is revealed by long-term experiments that the ZIF-8 membrane has good stability.?2?We propose a strategy for rapid in situ fabrication of ultra-thin zeolitic imidazolate framework-8?ZIF-8?hybrid membrane with assistance of two dimensional?2D?nanosheets at room temperature.The g-C₃N₄ nanosheets are synthesized by liquid exfoliation.The negatively charged g-C₃N₄ nanosheets with abundant nitrogen coordinating sites are capable to capture and anchor Zn²⁺and thus provide a large number of heterogeneous nucleation sites for the formation of initial ZIF-8 crystals.During the cyclical spin coating of the Zn²⁺/g-C₃N₄nanosheets and the ligand?2-methylimidazole?.The ZIF-8/g-C₃N₄ membrane with thickness of²40 nm can be obtained using this strategy within 30 min at room temperature,which is attractive for fast and facile preparation of molecular sieving membranes.Moreover,it exhibits promising H₂/CO₂ separation performance with the selectivity up to 42,which is superior to many other ZIF-8 membranes,while the flux of H₂ is 6.7×10^-8 mol m^-2 s^-1 pa^-1.