Metalorganicframeworksbasedmixedmatrixmembranesfor

ReviewMetal-organicframeworksbasedmixedmatrixmembranesforpervaporationZhiqianJia*,GuorongWuLabforMembraneTechnology,CollegeofChemistry,BeijingNormalUniversity,Beijing100875,ChinaarticleinfoArticlehistory:Received29May2016Receivedinrevisedform2August2016Accepted10August2016Availableonline13August2016Keywords:Metal-organicframeworksMixedmatrixmembranesPervaporationReviewabstractMetal-organicframeworks(MOFs)/polymermixedmatrixmembranes(MMMs)havegreatpotentialinpervaporationseparationduetotheeaseofdesignandmodificationofMOFs,alongwiththecompat-ibilitybetweenMOFsandpolymermatrix.ThisarticlereviewsthecurrentstatusofMOFsMMMsforpervaporation,includingpolymer(hydrophobicity/hydrophilicity,structurestability),MOFs(stability,hydrophobicity/hydrophilicity,surfacefunctionalstructure,particlesmorphologyandporessize),masstransfer,andapplications(dehydrationoforganicsolvents,removalofdiluteorganiccompoundsfromaqueousstreams,separationoforganic-organicmixtures,andmembranereactor).TheperspectivesandsuggestionsofMOFsMMMsaregiven.©2016ElsevierInc.Allrightsreserved.1.IntroductionPervaporation(PV)isconsideredasoneofthemostpromisingtechnologiesforliquidseparationsinbio-refinery,petrochemicalandpharmaceuticalindustries.Whenaliquidmixtureisincontactwithonesideofthemembrane,componentsareabsorbedbythemembrane.Theabsorbentsdiffusethroughthemembraneandevaporateaspermeatesontheothersideofthemembrane,inducedbyavacuumorgaspurge.Theseparationofcomponentsisachievedbythedifferenceinsorptionanddiffusion.Pervaporationusuallydealswiththeminorcomponentsoftheliquidmixture,anddemonstratesincomparableadvantagesintheseparationofheat-sensitive,close-boiling,andazeotropicmixturesduetoitsmildoperatingconditions,energyefficiency,easeofoperation,eco-friendliness,andhighseparationefficiency[1].TheapplicationsofPVcanbedividedintofourmaincategories:dehydrationoforganicsolvents,removalofdiluteorganiccompoundsfromaqueousstreams,separationoforganic-organicmixtures,andreversiblereactions.PolymermembraneshavebeenwidelyemployedinthePVprocess,buttheswellingofpolymermaterialsusuallyleadstothereductionofselectivityduetoaplasticizationeffect.Therefore,mixedmatrixmembranes(MMMs),composedofapolymerandinorganicfillers,wereproposedtoenhancethePVperformancebyimprovingtheselectivesorption,diffusionandstabilityviaincor-porationofappropriatefillers.ThefabricationprocessesofMMMsarebasedonwell-establishedpolymermembranetechnologies.However,theweakinterfacialbonding,incompatibilityandmis-matchingofthethermalexpansioncoefficientbetweentheinor-ganicfillersandpolymericphasesoftenresultsingrainboundarydefectsandthenadecreaseintheselectivityofMMMs.Atrade-offbetweenpermeabilityandselectivityoftenoccurs[2].Metal-organicframeworks(MOFs)arecrystallinenanoporousmaterialscomposedofmetalcentersandorganiclinkers.MOFshavereceivedremarkableattentionduetotheirunprecedentedproperties,suchaschemicalversatilitycombinedwithdesignableframeworktopologies,highsurfacearea,thermalstability,andpermanentporosity.MOFshaveanumberofpotentialapplicationsingasstorage[3],chemicalseparations[4],catalysis[5],adsorption[6],chromatography[7],drugdelivery[8],andmolecularsensing[9],etc.Incomparisonwithinorganicfillers,MOFshavebettercompatibilitywithpolymermatrixduetothepresenceoforganicligands.[Cu2(bza)4(pyz)n]wasthefirstMOFappliedasfillersinPVmembranes[10].ComparedwiththebarePDMSmembrane,aloadingof3wt%[Cu2(bza)4(pyz)n]showedaseparationfactorin-creaseofabouttwotimesinthePVof5wt%ofethanolaqueousmixturesatroomtemperature.TheMOFs-basedMMMscanbedividedintotwocategories:chemicallybondedmembranesandphysicallydopedmembranes.Forchemicalbondedmembranes,MOFsbondwiththepolymericmatrix.Forphysicallydopedmembranes,onlynon-covalent*Correspondingauthor.E-mailaddress:[e-mail](Z.Jia).ContentslistsavailableatScienceDirectMicroporousandMesoporousMaterialsjournalhomepage:://dx.doi.org/10.1016/j.micromeso.2016.08.0081387-1811/©2016ElsevierInc.Allrightsreserved.MicroporousandMesoporousMaterials235(2016)151e159interactions(dispersion,polarity,hydrogen-bonds)existbetweenMOFsandpolymericmatrix.AlthoughtherewereseveralexcellentreviewarticlesfocusingonPV,suchaspolymericmembrane[1],anddehydration[11,12],thereisnoreviewabouttheemergingMOFs-basedMMMsforpervaporation.ThisarticlereviewstheprogressintheMOFsMMMsforPV,includingthescreeningstra-tegiesforpolymerandMOFs,masstransfer,andapplications.ItishopedthatthisarticlewillprovideacomprehensiveoverviewofthecurrentstatusofMOFsMMMsinPV,andopennewperspec-tivestowardthedevelopmentofMOFsMMMswithmuchimprovedperformances.2.PolymerPolymermatrixisthemainpartofMMMs.Thepolymerprop-erties(hydrophobicity/hydrophilicity,structurestability)arecrucialforthePVperformanceofMMMs.2.1.Hydrophobicity/hydrophilicityInthecaseofsolventdehydration,thepolymersusuallyneedtohavehighsorptioncenters(e.g.,chargedsites)forwater,aswellasstructuralrigidityandregularityforselectivediffusion[13].Hy-drophilicmembranessuchaspoly(vinylalcohol)(PVA),chitosan,andpolyacrylonitrile(PAN)areoftenusedbecausethey