金属有机骨架材料(MOFs)PPT课件

MetalOrganicFrameworks,TeamMembers:CaoChangFuChuXianReporter:DuMengYuan,1,.,PublishedonNatureReviewsMaterials,2,.,CONTENTS,3,.,Introduction,1,4,.,Metalorganicframeworks(MOFs)areascientificallycompellingandfunctionallyevolvingclassofmeso-,micro-andultramicroporousmaterials.MOFstructuresencompassdozensoftopologies,includingseveral,suchassodaliteandRho,thatarealsowellknownforzeolites.MOFshavebeenexploredformanyapplicationsincluding,butnotlimitedto,gasstorageandrelease,chemicalseparations,drugdelivery,catalysis,lightharvestingandenergyconversion,and,recently,thedegradationoftoxicsubstancessuchaschemicalwarfareagents,5,.,MOFsarecomposedofmetalnodesandorganiclinkersthatcanbesystematicallytunedintermsofchemicalcompositionandprecisearrangementanattributethatdiffersfrompurelyinorganiczeolites,whichconsistlargelyofsiliconoraluminiumionslinkedbyoxygenatoms.,6,.,Inrecentyears,thenumberanddiversityofMOFstructureshavegrownsignificantly,andmanywater-stableandthermallystableMOFsnowexist,Enablinganexcitingexpansionoftheirapplication.Dependingontheapplicationenvisaged,differentfunctionalstabilitiesareimportant.,7,.,Stabilityofmetalorganicframeworks,2,8,.,Stabilityisdefinedasresistanceofthestructuretodegradation.However,anotherpossibledefinitionisthermodynamicinorigin:manyfunctionallystableMOFs(aswellaszeolites)arethermodynamicallyunstablewithrespecttoalternativetypically,denserpolymorphs.AnactiveareaofMOFresearchisthedevelopmentofroutestothermodynamicallyunstable,butfunctionallystable,polymorphs.,9,.,Stabilityofmetalorganicframeworks,10,.,1,Chemicalstability,ThegreatestconcernsfortheimprovementofMOFchemicalstabilityhavebeenlargelyrelatedtoliquidwaterandwatervapour;accordingly,wefocusonaqueoussolutions.InmostMOFstructures,thechemicalweakpointsareatthenodesmorespecifically,themetallinkerbondswithhydrolysisyieldingaprotonatedlinkerandahydroxide(orwater)ligatednode.Acidicsolutionscanacceleratetheformationoftheformer,andbasicsolutionscanacceleratetheformationofthelatter.AlthoughthereisnostandardmethodforassessingthestabilityofMOFsinacidic,basicorneutralsolutions,itisoftenjudgedbycomparingthepowderX-raydiffraction(PXRD)patternofaMOFbeforeandaftersoakingitinagivenaqueoussolution.,11,.,Thechemical(acidbase)stabilityofsomerepresentativemetalorganicframeworksbasedonliteraturedata.ThebarlengthindicatesthepHrangethatthemetalorganicframeworks(MOFs)cantolerate.AnarrowindicatesthattheMOFcanwithstandpH14.,12,.,Selectedsectionsofrepresentativemetalorganicframeworkmaterialsa|ZIF-8b|Cu-BTTric|MIL-53(Al)d|MIL-101(Cr)e|PCN-426-Cr(iii)f|(CH3)2NH22Eu6(3-OH)8(1,4-NDC)6(H2O)6.,13,.,ConnectivityofZr6nodesinzirconium-basedmetalorganicframeworksandtheassociatedcarboxylatemoleculesrequiredtolinknodestogether.,14,.,2,Thermalstability,ThermaldegradationofMOFsis,inmostcases,aresultofnodelinkerbondbreakage,accompaniedorfollowedbylinkercombustion.Asaconsequence,thermalstabilityisgenerallyrelatedtonodelinkerbondstrengthandthenumberoflinkersconnectedtoeachnode.Frameworkcatenationmorespecifically,interpenetrationorinterweavingofnetworkscanenhancestabilitythroughfavourableframeworkframeworkinteractions.Thermogravimetricanalysis(TGA)andinsituPXRDarebothtechniquesthatcanbeusedtogaugethethermalstabilityofMOFs.,15,.,3,Hydrothermalstability,Experimentally,hydrothermalstabilityisassessedbyexposingMOFstosteamatvariouspressuresandtemperatures,followedbyPXRDanalysisandporosityorsurface-areameasurements.MOFhydrothermalstabilitycanbeenhancedbyintermolecularorintramolecularforces,suchasinternalhydrogenbondingorstacking.ZIFsasaclasscompriseexcellentexamplesofhydrophobicMOFs,andmanyZIFsarehydrothermallystable,makingthemreasonablecandidatesforuseinhumidconditions.,16,.,4,Mechanicalstability,MOFsareknownfortheirextraordinaryporosityanattributethatinherentlydecreasesmechanicalstability.Therefore,asexpected,MOFsarelessmechanicallystablethanzeolites.Thisinstabilitycanmanifestitselfasphasechanges,partialcollapseofporesorevenamorphization,inresponsetomechanicalloading.SomearrangementsoflinkersandconnectorsrenderMOFsmoreresistanttodeformationanddestructionthanothers.Somecomputationalstudiesshowthatmechanicalstabilitytendstobeenhancedwithshorterlinkers.AnimportantpracticaldevelopmentthatgreatlyreducesthemechanicalperformancerequirementsforMOFsinapplications.,17,.,MOFstabilityincatalyticsystems,3,18,.,Thecatalyticactivesitecanbeseveraldifferentlocationswithinthestructure.ItcanbeincorporatedintheMOFlinkersornodes,orencapsulated,isolatedorstabilizedbyaMOF,orattachedtotheframeworkpostsynthetically.Regardlessofthemethodusedtointroducecatalyticallyactivesites,theframeworkmustbestableundercatalysisconditions.,19,.,MOFstabilityincatalyticsystems,20,.,1,Solution-phasecatalysis,Thiscanconstituteacidic,neutralorbasicconditions.Morespecifically,theMOFcatalystsneedtobeabletowithstandtheconditionsappropriateforthechosenreaction.,21,.,CatalyticoxidationofwaterusingIr-containingderivativesofUiO-67.TheimageshowsthestructureofUiO-67andIr-containinglinkers1and2thatareutilizedforwateroxidationcatalysisatpH1.,22,.,Catalytichydrolysisofthenerveagentsoman(knownasGD)byNU-1000,23,.,2,High-temperaturecatalysisofgas-phasereactions,TheuseofMOFsforgas-phasecatalysisisinanearlyphase,andmostinvestigationshavefocusedonproof-ofconceptreactionssuchastheoxidationofCOtoCO2.WebelievethatthenotionofMOFsasstableanduniformsupportsforsingle-sitecatalystsisanespeciallyexcitingone,meritingfurtherdevelopment.,24,.,OxidativedehydrogenationofcyclohexenetobenzeneusingV-UiO-66asacatalyst,25,.,Futureperspectives,4,26,.,Thee