Facilitydirectspace

AChromiumTerephthalate–BasedSolidwithUnusuallyLargePoreVolumesandSurfaceAreaG.
Ferey,1,2*C.
Mellot-Draznieks,3C.
Serre,1F.
Millange,1J.
Dutour,1S.
Surble,1I.
Margiolaki4Wecombinedtargetedchemistryandcomputationaldesigntocreateacrystalstructureforporouschromiumterephthalate,MIL-101,withverylargeporesizesandsurfacearea.
Itszeotypecubicstructurehasagiantcellvolume(702,000cubicangstroms),ahierarchyofextra-largeporesizes(30to34angstroms),andaLangmuirsurfaceareaforN2of5900T300squaremeterspergram.
Besidetheusualpropertiesofporouscompounds,thissolidhaspotentialasananomoldformonodispersenanomaterials,asillustratedherebytheincorpo-rationofKegginpolyanionswithinthecages.
Porousmaterialswithlarge,regular,accessiblecagesandtunnelsareincreasinglyindemandforapplicationsincatalysis(1),separations(2),sensors,electronics,andgasstorage(3,4).
De-pendingontheirstructureandporesize,thesematerialsallowonlymoleculesofcertainshapesandsizestoenterthepores.
Further-more,giantporesmayactasnanoreactors,inwhichtheconfinedvolumemaygeneratere-actionsthatdonotoccurinthebulkmaterial,orasnanomoldsforcalibratedandmono-dispersenanomaterials(5).
Inthisrespect,thelargerthepores,thewidertherangeofre-actantsthatcanbecombinedorstored.
However,thedesignofmaterialswithincreasinglylargeporescarries,especiallyformetal-organicframeworks,theriskofinter-penetrationoftheskeletonswithinstructures.
Inaddition,althoughthestructuralcharacteri-zationofsuchsolidswithlargecellsisusuallypossiblewhensinglecrystalsareavailable,theprobabilityofgettingthesolutionsisknowntodrasticallydecreaseoreventobecomezerowhenthecelldimensionsincreasetoomuch(6).
Theseproblemshaverestrictedthenum-berofdiscoveredporoussolidswithextra-largepores,ofwhichcloverite,withacellvolumeof125,000)3andporediameterscloseto30)(7)isthelargest.
Werecentlydevelopedastrategytoover-cometheselimitationsbasedonthecombina-tionoftargetedchemistryandcomputersimulations.
Hybridporoussolidsresultfromthethree-dimensional(3D)covalentconnectionofinorganicclustersandorganicmoietiesthatactaslinkers,andthefirststepinourBtailor-made[approachistocontrolthenatureoftheinorganicclusterandthechemicalconditionsrequiredforitsformationandstabilityinsolution(8).
Inthesecondstep,weusecom-putationalstrategies,typicallyourglobalopti-mizationAASBU(automatedassemblyofsecondarybuildingunits)method(9–12),asrecentlyadaptedtohybrids(13),orothercloselyrelatedmethods(14).
TheAASBUmethodexploreshowaninorganicclusterandanorganiclinker,orevenpredefinedhybridbuildingblocks,mayconnectin3Dspacetoformperiodiclattices.
Avirtuallibraryofcan-didateframeworksisproduced,alongwiththeircrystallographicfeatures(spacegroup,cellpa-rameters,atomiccoordinates)andtheirsimu-latedx-raydiffraction(XRD)patterns.
Thecomparisonofthesimulatedpatternofeachcandidatestructurewiththeexperimentaloneidentifiesthetargetedexperimentalstructure,givingdirectaccesstothestructuralsolutionwithoutanyrecoursetosinglecrystals.
Thefi-nalstructureisrefinedwiththeRietveldmethodfrompowderdata,theguestspeciesbeinglo-calizedfromFourierdifferencemaps.
Whiletacklingtheunderlyingissueofpolymor-phismofhybridmaterials,ourcomputationalapproachprovidesadirect-spacetoolforsolv-ingstructuresthatmaybehighlycomplex.
Toimplementourcombinedmethod,wefirstdetermined(10)theadequatechemicalcon-ditionsleadingtotheexistenceoftrimericinorganicbuildingblocks,formedbytheassem-blyofthreeoctahedrasharingam3-Ocommonvertex.
Simulationswerethenperformedtocombinetheseinorganictrimersin3Dspacewith1,3,5-benzenetricarboxylate(BTC)throughtheassemblyofacomputationallydesignedhybridbuildingblock.
Amongthevariouspredictedcrystalstructures,onecandi-dateexhibitedthesamepowderXRDpatternasthepowderedchromiumtrimesateMIL-1001InstitutLavoisier,CNRSUniteMixtedeRecherche8637,UniversitedeVersaillesSt-QuentinenYvelines,45AvenuedesEtats-Unis,78035VersaillesCedex,France.
2InstitutuniversitairedeFrance,103,BoulevardSaint-Michel,75005Paris,France.
3RoyalInstitution,21AlbemarleStreet,LondonW1S4BS,UK.
4EuropeanRadiationSynchotronFacility,38042Grenoble,France.
*Towhomcorrespondenceshouldbeaddressed.
E-mail:ferey@chimie.
uvsq.
frFig.
1.
(A)Thecomputationnallydesignedtrimericbuildingblockchelatedbythreecarboxylicfunc-tions.
TheSTwasconstructedwith(B)terephthalicacid,whichlies(C)ontheedgesoftheST.
(D)Ball-and-stickrepresentationofoneunitcell,highlightingoneSTdrawninapolyhedronmode.
(E)Schematic3DrepresentationoftheMTNzeotypearchitecture(theverticesrepresentthecentersofeachST)withthemedium(ingreen,with20tetrahedra)andlarge(inredwith28tetrahedra)cagesdelimitedbythevertexsharingoftheST.
Chromiumoctahedra,oxygen,fluorineandcarbonatomsareingreen,red,andblue,respectively.
23SEPTEMBER2005VOL309SCIENCEwww.
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org2040REPORTSonSeptember6,2020http://science.
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org/Downloadedfrom(15)(MIL,Mat2rialInstitutLavoisier),reveal-ingagiantcellvolume(9380,000)3)andlargeporesizes(25to29))consistentwiththeveryhighsurfaceareameasurement(SLangmuir03100m2gj1).
Thishybridcrystalstructurewasthenrefinedfromsynchrotronpowderdata,al-lowingthefurtherlocalizationoftheguestmoities.
MIL-100showedthefeasibilityofcreatingsimulation-assistedchemicalstructures(16).
Withthatadressed,weinvestigatedothercarboxylates,hereterephthalicacidE1,4-benzenedicarboxylate(1,4-BDC)^combinedwithsimilartrimers.
ComparedtootherMOFs(metal-organicframeworks),theresultingsolid,MIL-101,hasthebestcharacteristicsintermsofcelldimensions(702,000)3),poresizes(29to34)),andsurfacearea(5900m2gj1).
ThesynthesisofMIL-101consistsinthehydrothermalreactionofH2BDC(166mgat1mmol)withCr(NO3)3.
9H2O(400mgat1mmol),fluorhydricacid(0.
2mlat1mmol),andH2O(4.
8mlat265mmol),for8hoursat220-C.
Thisreactionproducedahighlycrystallizedgreenpowderofthechromiumter-ephthalatewithformulaCr3F(H2O)2OE(O2C)-C6H4-(CO2)^3.
nH2O(wherenis25),basedonchemicalanalysis.
Theyieldbasedonchromi-umis50%.
AnalysisofthepowderXRDdataindicatesacubiccell(a89))andacloserelationshipwiththeaugmentedMobilThirty-Nine(MTN)zeotypestructureofMIL-100(17).
Forthesimulationprocess,acandidatehybridbuildingblock,madeonthesolebasisofitscompatibilitywiththeexper-imentalmetal:organicratioofthetargetedMIL-101,wascomputationallydesignedasasupertetrahedron(hereafternotedST)(Fig.
1).
Itwasmadefromthelinkageof1,4-BDCanionsandinorganictrimersthatconsistofthreeironatomsinanoctahedralenvironmentwithfouroxygenatomsofthebidendatedicarboxylates,onem3Oatom,andoneoxygenatomfromtheterminalwaterorfluorinegroup.
Octahedraarerelatedthroughthem3Ooxygenatomtoformthetrimericbuildingunit.
ThefourverticesoftheSTareoccupiedbythetrimers,andtheorganiclinkersarelocatedatthesixedgesoftheST.
Followingourpreviousstrategy(14),theSTbuildingblockswerecomputationallyassem-bled.
ThesizeoftheSTrequiresanexpansionofthecubicunitcell(spacegroupFd-3m)tomorethan85)beforetheconstructionprocess.
TheconnectionbetweentheSTwasestablishedthroughverticestoensurea3DnetworkofBcorner-sharing[supertetrahedrawithanaug-mentedMTNzeotypearchitecture(18)(Fig.
1)andillustratesourconceptofscalechemistry(19).
OncethestructureconstructionofMIL-101wascomputationallycompleted(74atomsperasymmetricunitwithouthydrogenatoms),themodelstructureofMIL-101wasdirectlyusedforfullstructuralrefinementwithsynchrotrondata(tableS1andfig.
S1)(20).
FreewatermoleculesfillingtheporeswerelocatedthroughsuccessiveFourierdifferences.
TheSTsaremicroporous(witha8.
6)freeapertureforthewindows),andtheresult-ingframeworkdelimitstwotypesofmeso-porouscagesfilledwithguestmolecules(Fig.
2).
Thesetwocages,whicharepresentina2:1ratio,aredelimitedby20and28ST(oneby20andoneby28)withinternalfreediametersof29)and34),respectively(Fig.
2).
Thesevaluescorrespondtoacces-sibleporevolumesof12,700)3and20,600)3,respectively.
Thelargewindowsofbothcagesmakethelatteraccessibletoverylargemolecules.
Thesmallercagesex-hibitpentagonalwindowswithafreeopen-ingof12),whilethelargercagespossessbothpentagonalandlargerhexagonalwin-dowswitha14.
5)by16)freeaperture(Fig.
2).
Thermogravimetricanalysisinair(fig.
S2)revealedthatMIL-101wasstableupto275-C.
X-raythermodiffractometryshowedthattheevacuationoftheguestmoleculesdidnotaffecttheframework.
WealsofoundthatMIL-101exhibitedveryhighuptakeofgases.
TheN2sorptionisothermonthede-hydratedsample(fig.
S3A)isoftypeIwithsecondaryuptakesatP/P00.
1andatP/P00.
2,wherePisgaspressureandP0issat-urationpressure,characteristicofthepresenceofthetwokindsofmicroporouswindows.
UsingtheDubinin-Raduskhvichequation,wefoundaporevolumenear2.
0(1)cm3gj1forMIL-101.
TheapparentBrunauerEmmerTeller(BET)andSLangmuirsurfaceareaarelargerthan4,100(200)and5,900(300)m2gj1,respectively(Fig.
3).
Theisothermsareproba-blyoverestimatingthetrueinternalsurfaceareaofMIL-101,butcomparisonstobemadewithrelatedmaterialsarepossible.
Toourknowledge,thehighestsurfaceareareportedforanycrystallineoramorphoussolidE4500m2gj1(Langmuir)^,wasobtainedwithMOF-177,aporoushybridsolid(20).
ThelargestandarddeviationsforthesurfaceareaofMIL-101comesbothfromexperimentalconsiderations(suchaserroronweightmeasurementsandpurityofthesample)andfromthechoiceofthepointsusedfortheBETorLangmuircalcula-tion(fig.
S3B).
Theas-synthesizedMIL-101solidexhibitsasmallerSLangmuirsurfaceareawithinthe4500to5500m2gj1rangebecauseofthepresenceofvariableamountsoffreeterephthalicacidoutsideandwithinthepores.
Anactivationtreatmentwasthusperformedtoreachthemaximalsurfaceareaandporevolume(21).
MIL-101isstableovermonthsunderairatmosphereandwasnotalteredwhentreatedwithvariousorganicsolventsatroomtem-peratureorundersolvothermalconditions.
Theseproperties,togetherwithhighadsorp-tioncapacities,makeMIL-101anattractivecandidatefortheadsorptionofgasorlargemolecules.
Theverylargewindowseasilyallowtheintroductionofnewspeciesintothecagesandpossibleenhancedreactionsfavoredbyconfinementeffects(similartoapressure)inthecages.
Moreover,assoonasintroducednanometricspeciesfillthevol-ume,thefixeddimensionsoftheporesleadFig.
2.
(AandB)Ball-and-stickviewandfreedimensions(A)ofthepentagonalandhexagonalwindows.
(CandD)Ball-and-stickviewofthetwocages.
Chromiumoctahedra,oxygen,fluorineandcarbonatomsareingreen,red,redandblue,respectively.
REPORTSwww.
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orgSCIENCEVOL30923SEPTEMBER20052041onSeptember6,2020http://science.
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org/Downloadedfromtomonodispersednanomaterialsonthescaleof1to3nm.
Thepossibilityoftheirintro-ductiondependsonthefitbetweentheirsizeandtheaccessibledimensionsofthewindowsofeachcage.
Largespeciesmaythereforeoccupyonlythelargecages(20,600)3)whileleavingspaceforotherspecieswithdifferentpropertiesinthesmallcages(12,700)3).
Suchaselectiveplacementofguestsmightleadtohithertounknownassembliesofmonodispersemultifunctionalnanomaterialsandthepossibilityofstructuralcharacterizationofthesenano-objectswhenthehoststructureisnotaffectedbytheintroductionofspecies.
Toillustratethisidea,weexploredthein-corporationofKegginpolyanionsinMIL-101.
Suchincorporationhasbeenachievedpre-viouslythroughtheencapsulationofamolyb-denumKegginanioninametal-oxygensystem(22).
TheK7PW11O40.
nH2Osaltwasselectedbecauseofitslowacidity,thepres-enceofa31Pnuclearmagneticresonance(NMR)nucleusforNMRcharacterization,andfinallyitssize(vanderWaalsradius,13.
1)),whichrulesoutthediffusionofKegginionsintothesmallcages.
ApowderedsampleofMIL-101wasplacedinanaqueoussolutionoftheKegginsaltfor2hours.
Toprobethepresenceofthepolynanionwithinthepores,theresultingMIL-101–Kegginsolidwasanalyzedbythermalgravimetricanalysis(TGA),N2sorptionmeasurement,XRD,31PsolidstateNMR(Fig.
4),andinfraredspectroscopy(fig.
S3).
AllofthesetechniquesconfirmedthepresenceofalargeamountoftheKegginionswithinthepores:astrongdecreaseintheweightlossesETGA(fig.
S2)^andsurfaceareasESLangmuir3,750(250)m2gj1insteadof5,900(300)m2gj1forMIL-101(fig.
S3C)^duetothehigherdensityoftheKegganmoietiescomparedtoMIL-101.
WeobservedsignificantchangesinXRDpeakintensitiesbutnotoftheBraggpeakpositions(fig.
S4).
InfraredspectroscopyconfirmedthepresenceofthepolyanionswithintheporesofMIL-101(fig.
S5).
31PNMRalsoindicatedonesinglepeakatabout–12.
2(1)partspermillion(ppm),confirmingthattheintegrityoftheKegginstructurewasretainedwithintheporesofMIL-101(fig.
S6).
Quantitativeanalysis(17)alsogaveanestimationof0.
05Kegginanionsperchro-mium.
ConsideringthesizeoftheK7PW11O40ion,weassumedthatthepolyanionscoulddif-fuseintothelargestcagesonly,whichwouldallowaboutfivehighlychargedKegginmoitiesperlargecage(Kegginpercage,5.
3).
BecausethevolumeofaPW11O407–anionisnearly2250A3,fiveKegginionsrepresent10,100A3involume,whichislowerthanthe20,600A3volumeofalargecage.
There-sidualvolumeisprobablyoccupiedbycationsandwatermolecules.
Thissuccessfulincorpo-rationofKegginanionsinlargeamountsstronglysuggeststhatMIL-101,acrystallizedhybridsolidwithaperiodicalandcalibratedporosity,isanexcellentcandidatefortheintro-ductionofgas(23)nano-objectsinaregularandmonodispersemodewithspecificphysicalproperties(24)orfordrugdelivery(25).
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Initialhydrogenstoragemeasurementswere0.
45and3.
75weightpercentat293Kand77K,re-spectively,at2MPa.
Thevaluesat77KseemtobethehighestforMOFsafterthecontestationofpre-viousresults(3).
24.
InitialintroductionofsemiconductingZnSnano-particlesintheporesofMIL-101wassuccessfullyachievedwithaZnS/Crratiocloseto0.
5.
25.
IncorporationofibuprofenwithinMIL-101hasbeenachievedinlargeamounts(1gofdrugpergramofMIL-101)withatotalreleaseofthedrugwithinafewdays.
26.
WethankF.
TaulelleandM.
HaouasforcollectingsolidstateNMR,M.
Latrocheforhydrogensorptionmea-surements,P.
MialaneforprovidingtheKegginsaltandforhelpfuldiscussions,S.
FloquetandE.
CadotforhelpfuldiscussionabouttheintroductionofZnSnano-particles,andP.
HorcajadaandM.
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SupportingOnlineMaterialwww.
sciencemag.
org/cgi/content/full/309/5743/2040/DC1MaterialsandMethodsFigs.
S1toS6TableS1ReferencesandNotes17June2005;accepted16August200510.
1126/science.
1116275Fig.
4.
(A)SchematicviewoftheinsertionofKegginanionswithinthelargestporeofMIL-101.
(B)XRDofMIL-101(1)andMIL-101(Keggin)(2).
q,indegrees.
(C)TGAofMIL-101(1)andMIL-101(Keggin)(2).
T,temperature(K).
(D)Nitrogensorption-desorptionisothermsat78KofMIL-101(1)andMIL-101(Keggin)(2).
Vads,volumeadsorbedincm3gj1.
(E)31Psolid-stateNMRspectraoftheKegginsaltandMIL-101(Keggin).
d,chemicalshiftinppm.
Fig.
3.
Nitrogengassorptionisothermat78KforMIL-101.
P/POistheratioofgaspres-sure(P)tosaturationpressure(P00750torr).
P/P000.
20.
40.
60.
81120010008006004002000Vads(cm3.
g-1)REPORTS23SEPTEMBER2005VOL309SCIENCEwww.
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org2042onSeptember6,2020http://science.
sciencemag.
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sciencemag.
orgSCIENCEErratumpostdate18NOVEMBER2005postdate18November2005ERRATUMCORRECTIONSANDCLARIFICATIONSReports:"Achromiumterephthalate–basedsolidwithunusuallylargeporevolumesandsurfacearea"byG.
Féreyetal.
(23Sept.
2005,p.
2040).
ThecrystalstructuredepositionnumberforMIL-101wasomitted;theCSDnum-beris415697.
Therewereerrorsinnote(23);itshouldread"Initialhydrogenstoragemeasurementwas4.
5weightpercentat77Kat3MPa.
ThisvalueseemstobethehighestforMOFsafterthecontestationofpreviousresults(3).
"Finally,thelastsentenceoftheFig.
1legendshouldread"Chromiumoctahedra,oxygen,fluorine,andcarbonatomsareingreen,red,red,andblue,respectively.
"onSeptember6,2020http://science.
sciencemag.
org/DownloadedfromAChromiumTerephthalate-BasedSolidwithUnusuallyLargePoreVolumesandSurfaceAreaG.
Férey,C.
Mellot-Draznieks,C.
Serre,F.
Millange,J.
Dutour,S.
SurbléandI.
MargiolakiDOI:10.
1126/science.
1116275(5743),2040-2042.
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