Synthesis Of Ordered Porous Poly(ionic Liquid)s And Their Application In Adsorptive Separation

Efficient separation of structurally similar compounds is an important research direction of chemical engineering.The design and development of porous materials with selective functional groups and ordered pore structures provide an opportunity for the development of energy-saving and efficient separation technology.Ionic liquids(ILs)have the characteristics of precise structure design and strong molecular recognition,and have shown good prospects in separation applications.In this dissertation,two types of ordered porous poly(ionic liquid)s(PILs)with ordered pore structure and high ionic density were constructed by developping new synthetic strategies.And the preparation process and pore size regulation,the adsorptive separation performance of natural active compounds and various gases were systematically studied.We explored a facile methodology via microphase separation,and prepared anion-functionalized mesoporous PILs(MPILs)with mesoporous structure and abundant carboxylate ILs.The effects of synthetic process parameters on pore structure and ionic liquid content were investigated.And the adsorption and separation performance of tocopherol homologues and phenolic homologues with highly similar structure were studied.The results showed that the pore size distribution of anion-functionalized MPILs was between 3.0 and 4.2 nm,and the IL content was higher than 0.78 mmol g"1.These PILs exhibited excellent separation performance of tocopherol homologues and phenolic homologues,and showed high adsorption capacity as well as separation selectivity,which are significantly better than those of commercial adsorbents and common MPILs.The adsorption capacity of tocopherol homologues can be as high as 211.5 mg g-1 and excellent selectivity is up to 8.65(Sδ/α)and 4.20(Sβ&γ/α).Porous PILs with hierarchical micro-mesoporous structure were further prepared via a microphase separation-hypercrosslinking strategy.We explored the effect of hypercrosslinking strategy on pore structure,and studied the separation performance of carbon dioxide/nitrogen(CO2/N2)and acetylene/ethylene(C2H2/C2H4).The results showed that hypercrosslinking treatment stabilized/rebuilt the labile collapsed mesoporous network and produced new micropores.Both the specific surface area and the pore volume were significantly improved.And the material exhibited enhanced gas adsorption capacity and good separation selectivity.Taking new amphiphilic ILs as monomers,we designed a covalent and ionic dual-crosslinking based methodology to fabricate ultramicroporous PILs with ordered ultramicroporosity.And we explored the influences of branched structure and anions on pore structure.Further,through the molecular dynamics simulation(MD)method,reasonable microstructure models of PILs and monomer were constructed,and the pore-forming mechanism was explored.The results showed that ultramicroporosity can be effectively formed via covalent and ionic dual-crosslinking.Pore size was narrowly distributed between 3.24 and 6.30 A.The enhancement of the branched structure can improve the ionic density,effectively increase the degree of crosslinking and enrich ultramicroporosity within narrow distribution.But Larger anion size resulted in a wider distribution of ultramicroporosity.These materials also showed superior stability,reusability and reproducibility.MD results showed covalent and ionic dual-crosslinking were key factors.It was verified that the improvement of the branched structure was beneficial to enhance the interconnected ultramicroporosity.Ultramicroporous PILs played as adsorbents,we studied the separation performance of C2H2/C2H4 and propyne/propylene(C3H4/C3H6),respectively.And we explored the influences of branched structure and anions,studied the separation performance of breakthrough experiments with the mixed gases of C2H2 and C2H4.The difference in the interaction between alkynes/olefins and ILs was revealed by quantitative calculations and MD.The effects of ultramicropore with narrow distribution and high ionic density on adsorptive separation performance were investigated.The results showed ultramicroporous PILs exhibited outstanding separation performance of C2H2/C2H4 and C3H4/C3H6.The acetylene uptake at 298 K amd 1 bar can reach 1.46 mmol g-1.The ideal adsorbed solution theory(IAST)selectivities could be up to 52.73 and 76.68,respectively,for C2H2/C2H4 mixtures containing 1%and 50%C2H2 at ambient conditions,which can be camparable with reported metal-organic frameworks(MOFs).Enhancement of the branched structure significantly increased the adsorption capacity of olefins,and the stronger the basicity of the anion,the higher the separation selectivity of the alkynes/olefins.Besides,breakthrough experiments verified that the ultramicroporous PILs had excellent C2H2/C2H4 separation performance and recycle performance.MD showed that high ionic density and narrow distribution of ultramicroporosity are the key to achieve high separation performance of alkynes and olefins.The stronger H-bond interaction between the anion and the alkyne,the higher the separation selectivity,and the abundant ultramicropores can effectively enhance the adsorption capacity of the alkyne.High adsorption capacity and selective separation of sulfur dioxide(SO2)were carried out by using ultramicroporous PILs.The adsorption equilibrium,breakthrough experiments and separation mechanism were studied.The results showed that high capacity for SO2 was realized by using ultramicroporous PILs at ambient conditions(8.12 mmol g-1,at 298 K and 1 bar).And ultramicroporous PILs had excellent adsorption performance at low pressure(at 0.002 bar,1.55 mol g-1).Besides,ultramicroporous PILs exhibited outstanding separation performance for SO2/CO2,SO2/CH4 and SO2/N2.The excellent separation performance of materials were further confirmed by the experimental breakthrough studies.In addition,the molecular simulation results demonstrated that the strong interaction between the ILs and the SO2 molecule achieved the ultra-high separation selectivity of SO2,and the richer ultramicroporosity in the materials,the higher the SO2 adsorption capacity.