Molecular Separation Function Led Pore Design And Synthesis Of Porous Organic Frameworks And Related Membranes

Separation plays an essential role in industry and our daily life,involving processes such as distillation,crystallization,concentration,and purification.However,these traditional separation technologies are typically accompanied by high energy consumption and high pollution.In 2016,the study found that distillation alone accounted for 10-15%of the world's total energy consumption.Therefore,developing alternative separation techniques with low energy consumption and environmental friendliness would decrease the global energy consumption and environmental pollution.Adsorption-based and membrane-based technologies have attracted increasing attention and demonstrated great potential in industrial processes due to their advantages such as high efficiency,easy operation,low energy consumption and environmental sustainability.Herein,in this paper,we focus on the targeted synthesis of porous organic frameworks and membranes with excellent separation performances,elucidating the relationship between the structure/property of materials and the separation function of adsorption and membrane.The main contents are in the followings:1.In order to obtain porous organic frameworks with efficient Xe/Kr separation,we present a targeted synthesis of ultra-microporous organic frameworks with sulfonate groups.The results reveal that the addition of sulfonate groups in PAF-45S not only reduce the pore size distribution in parent materials(PAF-45),but also increase the polar adsorption sites in frameworks,which can realize xenon synergistic adsorption.The theoretical simulation further explains the mechanism between sulfonate adsorption sites and xenon molecule,which is consistent with experimental results.PAF-45S is robust and reproducible in terms of Xe capture,holding it great promise for application in Xe/Kr selectivity.2.Most porous organic frameworks face the limitation in adsorption and separation of macromolecules due to their only microporous structures.We report a new synthesis strategy called hard-template synthesis which uses mesoporous silicas(SBA-15 and B56-E-20)as the hard templates,biphenyl as the single organic precursor.PAF-45@SBA-15 and PAF-45@B56-E-20 are prepared by in-situ coupling biphenyl within the voids of mesoporous silica.After etching silica,two micro-mesoporous organic frameworks(PAF-45HX)are successfully prepared.The resulting micro-mesoporous organic frameworks exhibit the intrinsic microporosity and controllable mesoporous size,which lead to the promotion of macromolecules separation and capture.PAF-45HS possesses higher Rhodamine B adsorption than PAF-45 in terms of maximum uptakes and rate constants.A simple and general synthesis strategy of hard-template provides guidance on developing new-type micro-mesoporous organic frameworks.3.In an effort to enhance the reverse osmosis performance of thin membrane under the low pressure,a viable approach of screen printing is introduced to direct the synthesis of crack-free and stable porous organic framework membranes(Tp Pa(OH)₂).Due to the sieving function of screen in gel precursor,the screen printing synthesis approach is more advantageous over classical techniques in fabricating smooth and uniform POF membranes.The shape and the size of Tp Pa(OH)₂ membrane can be precisely controlled by adjusting the screen size and print cycles.With the aid of growth mechanism in Tp Pa(OH)₂ membrane,the effect of formation process on Tp Pa(OH)₂membrane was investigated by XRD and SEM.The desalination performance shows high water permeance(1.4 L m^-2 h^-1 bar^-1)and appreciable ion exclusion(Na⁺,62.9%)owing to its hydrophilic pores in a suitable size.This study provides a guideline for the fabrication of high-quality POF membranes,and sheds light on the potential applications of POF membranes for water desalination.