Interactions of an Imine Polymer with Nanoporous Silica and Carbon in Hybrid Adsorbents for Carbon Capture - Rother et al. - 2021 - Unkn

《Interactions of an Imine Polymer with Nanoporous Silica and Carbon in Hybrid Adsorbents for Carbon Capture - Rother et al. - 2021 - Unkn》由会员上传分享，免费在线阅读，更多相关内容在学术论文-天天文库。

pubs.acs.org/LangmuirArticleInteractionsofanIminePolymerwithNanoporousSilicaandCarboninHybridAdsorbentsforCarbonCaptureGernotRother,*UmaTumuluri,KuanHuang,WilliamT.Heller,ShengDai,Jan-MichaelCarrillo,andBobbyG.SumpterCiteThis:Langmuir2021,37,4622−4631ReadOnlineACCESSMetrics&MoreArticleRecommendations*sıSupportingInformationABSTRACT:Efficientcarboncapturefromstationarypointsourcescanbeachievedusinghybridadsorbentscomprisingnanoporoussubstratescoatedwithiminepolymers.ThephysicalpropertiesoftheCO2-adsorbing,nanodispersedpolymersarealteredbytheirinteractionswiththesubstrate,whichinturnmayimpacttheircapturecapacity.Westudysilicaandcarbonnanoporoussubstrateswithdifferentporemorphologiesthatwereimpregnatedwithpolymeriminewiththegoalofcharacterizingthepolymerdispersionsinthepores.Forsilicaandcarbonsamples,themeandensitiesofconfinedpoly(ethyleneimine)(PEI)weremeasuredasfunctionsofpolymerloadingandtemperatureusingsmall-angleneutronscattering.Strongdensificationisfoundforiminepolymersimbibedinmesoporouscarbon.PEIinnanoporoussilicadoesnotexperiencethisstrongdensification.Athighloadings,plugsform,preferablyattheporethroats,andcanreduceaccessibleporosity.CO2capturemeasurementsshowthatPEIinteractionswiththesubstrateplayanimportantrole.PEIincarbonshowsthehighestcapturecapacityatlowtemperaturesandthelowestCO2adsorptionathightemperatures,makingitwell-suitedfortemperatureswingadsorptionapplications.■INTRODUCTIONtemperaturemaythusbecausedbythermalexpansionorincreasedchainmobilityofPEIinthepores,resultinginCO2isanimportantgreenhousegas,andtechnologiesforitsenhancedkineticsofCO2adsorptionatelevatedtemper-captureandutilizationareactivelyresearched.CO2canbe17,18atures.Inrecentstudies,wemeasuredthenanostructureofremovedfromnaturalgasesaswellasfluegasesbyabsorptionporePEIandself-diffusiondynamicsofthePEIlayerintheusingsolvents,adsorptionusingsolidadsorbents,and19,201−3narrowporesofnanoporoussilicasubstrates.Theself-separationusingmembranes.AmongtheseprocessdiffusiondynamicsofPEIinSBA-15aresloweddownwithtechnologies,adsorptionusingsolidadsorbentsstandsoutrespecttobulkPEI,indicatingadhesiontothesubstrate.DownloadedviaUNIVOFCONNECTICUTonMay16,2021at09:23:50(UTC).foritslowenergyuseforsorbentregeneration,higherCO24,5HydrophobicmodificationofSBAledtoanincreaseinself-capturecapacity(CC)andselectivity,andeaseofhandling.diffusiondynamics,which,however,remainedslowerthanbulkAminesformcarbamicacidwithCO2inreversible21Seehttps://pubs.acs.org/sharingguidelinesforoptionsonhowtolegitimatelysharepublishedarticles.6dynamics.Holewinskietal.studiedd-PEIinnanoporousreactionswhichmakestheminterestingcarbon-captureSBA-15silica.Analysisofsmall-angleneutronscatteringcandidates.KeytothehighCCperformanceisalarge7(SANS)datashowedthatPEIinitiallyformsfilmsattheadsorbentsurfacearea,whichcanbeengineeredinseveralporewalls,andathigherPEIloadings,plugsarealsoformed.ways.MicrostructuredaminesubstratesshowhighCCand8Inthisstudy,wefocusoninteractionsofpore-confinedPEIgoodstabilityagainstwaterdegradation.Amine-function-withsilicaandcarbonsubstrates.WhileweincludeSBAalizednanoporousadsorbentsareinvestigatedfortheirhigh4,9−11samplessimilartothosestudiedinref16,wealsostudyCO2capturecapacities.Poly(ethyleneimine)(PEI)-controlledporeglass(CPG)anddisorderedmesoporousfunctionalizedadsorbentsaresuitableforCO2capturefrom12−16carbon(DMC)substrates.Thesenanoporoussolidsaremorebothfluegasesandambientair.TheirCO2adsorptionrobustthanSBAagainstwatervapor,whichmightbeusefulinbehaviorisalsoscientificallyinterestingbecausesomePEI-impregnatedsilicasorbentsarereportedtoadsorbmoreCO2atelevatedtemperaturesthanatroomtemperature.16−18ItisReceived:February1,2021speculatedthatthehighlybranchedstructureofthetypicallyRevised:March20,2021usedlow-molecular-weightPEIcausesslowdiffusionofCO2Published:April5,2021insidetheporesofthesorbents,andareducedlow-temperatureCO2CCmayresultifallaminegroupsarenotaccessibletoCO2.ThereportedincreaseinCO2CCwith©2021AmericanChemicalSocietyhttps://doi.org/10.1021/acs.langmuir.1c003054622Langmuir2021,37,4622−4631

1Langmuirpubs.acs.org/LangmuirArticleaTable1.CharacterizationofBareandImpregnatedAminopolymerSupports,LiquidN2Sorption,andTGAporevolumesurfaceareamesoporevolumemesoporeradiusmicroporevolumePEIcontentsample(cm3/cm3)(m2/cm3)(mL/cm3)(nm)(cm3/cm3)(g/cm3)SBA0.6255000.562.770.0610SBA-L0.4252590.422.5900.116SBA-M0.1751160.1532.180.0210.302SBA-H0.125740.1182.060.0060.524CPG0.5521380.5266.070.0270CPG-L0.4541060.4395.520.0150.056CPG-M0.365840.3555.240.010.134CPG-H0.227450.2175.10.010.274DMC0.5033410.4543.010.0450DMC-L0.3281650.3052.830.0210.079DMC-M0.2521210.2412.710.010.143DMC-H0.098400.0872.570.010.279aAllquantitiesarenormalizedtothesamplevolume.12h.A12.22mg/cm3solutionofD-PEIinMeOD(deuteratedwetCO2applications.Themorphologyofporepolymerisimpactedbyadsorptionandporeconfinementeffects,whichmethanol)wasmixedwithpureMeODtoyieldatotalvolumeof30cm3(preciseratiosofliquidsadjustedtocreatespecificpore-fillingcanleadtomassdensitychanges.Thesemorphologicalchangescanalsoimpactotherpolymerproperties,includingvaluesarelistedinTableS1).Themesoporousmaterial(ca.0.3g)wasaddedtothissolution,andtheslurrywasstirredfor3hatroommobilityandCO2CC.EvaluationoftheSANSdataiscarriedtemperature.Thesolventwasremovedunderalightvacuum,afteroutintandemwithotherexperimentalandcomputermodelingwhichthesamplewasdriedat110°Cina10mbarvacuumfor12h.characterizationtoprovidethePEImassdensitiesandnano-NominalPEIloadingsofporespacesof10%(L),25%(M),and50%morphologiesfordifferentporeenvironments,porefillings,(H)werepreparedforthethreesubstratesandcharacterizedusingandtemperatures.Specifically,SANSdataareanalyzedforliquidN2sorption,thermogravimetricanalysis(TGA),andSANS.theirscatteringinvariant,yieldingthemeandensityofporeThroughoutthepaper,namesofthesamplesareformedbyaPEI,whichcandeviatesignificantlyfromitsbulkvalueduetocombinationofthemesoporousmatrix(SBA,CPG,andDMC)attractiveorrepulsivepolymerinteractionswiththeporefollowedbythedescriptorofsampleloadingwithPEI(empty,-L,-M,surfacesandconfinementeffects.Variationoftheporepolymer-H).Forinstance,SBAdenotestheemptySBAmaterial,whileSBA-LloadingchangesthefractionofpolymerindirectcontactwithdenotesSBAfilledwithalowamountofd-PEI.SorbentCharacterizationwithLiquidNitrogenSorption.theporewalls,andmeasurementsoftheporePEIdensitiesforNitrogensorptionmeasurementsat77Kwereperformedforboththedifferentloadingsinterrogatetheimpactofproximitytothenativeandamine-coatedsubstratesusingaMicrometricsTristar3020porewallsonthepolymerdensity.BymeasuringporePEIinstrument.Samplesweredegassedfor12hat110°Cpriortodensitiesasfunctionsofsubstratechemistryandmorphology,analysis.SurfaceareaswerecalculatedusingtheBrunauer−Emmett−pore-fillingdegree,andtemperature,amoredetailedunder-Teller(BET)model.Porevolumesandporesizewerecalculatedstandingofthepolymer−substrateinteractionsisobtained,usingtheliquidnitrogenuptakeatP/P0=0.98andthemodifiedwhichwillinformourunderstandingandaidindesigningmoreKelvinequationonthedesorptionbranches.Thenitrogenefficienthybridadsorbents.Theultimateobjectiveofthisstudyadsorption−desorptionisothermsat77KareshowninFigureS1istodeterminetherelationshipsbetweenthephysicalstatesofintheSupportingInformation.porePEIanditsCOcapturecapacities.ThesubstratesPEIUptakebyMesoporousSubstrates.PEIcontentsofthe2studiedaretwonanoporoussilicasamples,SBA-15(“SBA”)silicasamples(SBAandCPG)weremeasuredusingaNetzschSTA409PGTGA/differentialscanningcalorimetry(DSC)instrument.andCPG-10-75(“CPG”)with5.4and13nmporesizes,Weightlosseswerecalculatedfromthedatatakenat(120−900)°C,respectively,andonedisorderednanoporouscarbonsample33usingacombinedflowof90cm/minofairand30cm/minofwith6nmporesize(“DMC”).Thesewell-characterizednitrogen.Datawerecollectedat(25−900)°Cusingaheatrateof10materialsserveasproxiesforawidevarietyoftargetmaterials°C/min.PEIcontentofthemesoporouscarbon(DMC)sampleswasforcaptureapplications.AlthoughsimilarSBAsampleswerecalculatedusingCHNelementalanalysis(AtlanticMicrolabs).alreadystudiedinref16,weutilizeanovelanalysismethodCO2Adsorption.CO2capacitiesweremeasuredusingaTAInstrumentsQ500TGA.Sampleswerepretreatedundera100cm3/anduseSBAasthebenchmarkandreference.WewillcompareourSBAresultstothoseobtainedinref16intheConclusionsminflowofheliumat110°Cfor3h.Thesampleswereexposedtosection.10%CO2/90%Hefor6h.TheCO2uptakewascalculatedfromthegaininmassafterexposuretoCO2inhelium.TheCO2uptakewasmeasuredatadsorptiontemperaturesof30and80°C.■EXPERIMENTALSECTIONSANSExperiments.SANSexperimentswereperformedattheSorbentSynthesis.DeuteratedPEI(d-PEI)waschosenfortheEQ-SANSinstrumentattheSpallationNeutronSourceatOakRidge22SANSexperimentstoobtainagoodcontrastbetweentheamineNationalLaboratory.Threeinstrumentconfigurationswereusedtochainsandvoidspacespresentinthesorbentswhilealsominimizingcoverawiderangeofmomentumtransfers(Q).LowQdatawereincoherentscatteringcontributions.Theutilizedd-PEIwithaacquiredusingan8msample-to-detectordistance,10−12.6Åmolecularweightofca.1000g/molwassynthesizedbytheJonesneutronwavelengthband,and10mmsourceaperture.MediumQgroupatGeorgiaTechUniversity.Theratiosofprimary,secondary,datawereacquiredwitha4msample-to-detectordistance,a10−13.2andtertiaryaminesare20:48:32.AfullcharacterizationofthisÅneutronwavelengthband,anda25mmsourceaperture.HighQmaterialisprovidedinref16.Theamine-functionalizedsorbentsweredatauseda2msample-to-detectordistance,a2.5−6.1Åneutronpreparedbywetimpregnationusingawell-definedprotocol:wavelengthband,anda25mmsourceaperture.Theneutronsubstrateswerefirstdriedat110°Cunder10mbarofvacuumforchopperswereoperatedat60Hz.Samplesweremeasuredinsealed4623https://doi.org/10.1021/acs.langmuir.1c00305Langmuir2021,37,4622−4631

2Langmuirpubs.acs.org/LangmuirArticlefusedsilicaglasscells(HELLMA“banjocell”)witha1mmpathTherefore,thevolumeof1gofSBAequals0.75cm3+1g/2.2length.Theobtainedscatteringcurveswerecorrectedforbackgroundg/cm3=1.204cm3.ForCPGandDMC,thevaluesare1.01andtransmissionandradiallyaveraged.Thescatteringcurvesfromtheand0.914cm3/g,respectively.Likewise,amountsofporePEIdifferentinstrumentsettingsweremergedtogivescatteringcurvesin−1arealsonormalizedtosamplevolume(seeTable1).therangeofmomentumtransfersof0.00240.1Å−1withthefunctionI(Q)=m*Qa+bandsubtractingbfromthedata.■RESULTSPEIUptakeintoMesoporousSubstrates.Therespec-tiveamountsofphysisorbedPEIintheindividualsampleswerequantifiedusingacombinationofTGAandCHNanalysis,yieldingamineloadingpergramofmesoporoussubstratedata(summarizedinTable1).TheDSCdata,showninFigureS2,revealshiftsintheboilingpointsordecompositionofpore-confinedPEI.PEIconfinedinnanoporoussilicashowsdecreasingboiling/decompositiontemperaturesfromlowtoFigure1.CO2CCofPEI/CPG,PEI/SBA,andPEI/Csorbentsat30highloadings:inSBA,241,238,and231°CandinCPG,229,and80°C.218,and217°C.ItappearsthatPEI−silicasupportinteractionsstabilizetheliquidstateofthesurface-boundWefindthatCO2CCisgenerallyhigheratthelowerpolymerpossiblythroughbindingofaminegroupstosurfacetemperatureandthehighestincarbon-basedmaterialsatlowhydroxyls.temperatures.TheCCvaluesareoverallcomparabletotheNAdsorptionat77K.ThesupportsandPEI-92valuesreportedinarecentreviewarticle.TheCCvaluesforimpregnatedsampleswerecharacterizedusingliquidN2thesilicamaterialsaresimilarathigherloadingsofPEI,butsorption,showninFigureS1.ThederivedsurfaceareasandhigherCCvaluesaremeasuredintheCPGsubstratesatlowporevolumes,summarizedinTable1,showthatPEIindeedPEIcontents.Themajordifferencebetweenthetwosilicaenterstheporespacesofallsamples,reducingboththesamplesisthepresenceofmicroporesinSBA,whicharefilledaccessibleporevolumesandsurfaceareas.TheemptyCPGwithorblockedbyPEIaddedatevenlowloadings,assampleshowsH1hysteresistypicalfornanoporoussamplesmeasuredbythestrongreductioninmicroporevolume.withwell-defined,cylindricalporesandlowmicroporosity.ForIncreasesintemperatureledtoapronounceddropinCCattheemptySBAmaterial,H1hysteresisandasignificantlowPEIloading,whileCCisunaffectedathighloadings.portionofmicroporesarefound.ForemptyDMC,H2Incontrast,DMC-basedsorbentscombinehighCCatlowhysteresisisfound,indicatingadisorderedporesystemwithtemperatureswiththestrongesttemperaturedependencesofwideporesizeorshapedistribution.DMCalsohasallsamples,whichareexcellentpropertiesfortemperatureTSAmicropores.AdditionofsmallamountsofPEItoSBAandapplications.TheDMC−PEICCat30°Ciscomparableto26DMCsubstratesledtostrongreductionsinmicroporevolume,thevaluesreportedbyWangetal.,butnohigh-temperatureindicatingthatPEIinitiallyeitherfillsthemicroporesorclogsCCvaluesforPEIincarbonsupportscouldbefound.Themicroporeentrances.Inaddition,strongreductionsofthebaresilicatesupportsarepoorsorbents(bothadsorbinglessmesoporecondensationstepheightandtotalporevolumearethan0.1mmol/gofCO2).Incomparison,thebareobservedupontheadditionofPEI.TheformationofPEImesoporouscarbonisabettersorbentforCO2(0.33mmol/layersattheporewallsleadstoreductionsoftheeffectiveporeg),asreportedintheliterature.23radiimeasuredbyliquidnitrogenadsorption.ContinuousSANSExperiments.SANSwasusedtocharacterizethedecreasesofeffectiveporeradiiwithincreasingamountsofPEIporoussubstratesandPEIphasescontainedinsidethewereobservedinallsamples,indicatingadsorbedlayernanopores.Small-anglescatteringiscommonlyusedtoformationgrowthwiththeadditionofPEIinallsubstrates.measuresizes,shapes,andorientationsofnanoscaleobjects,ThecharacterizationsprovidedinTable1arenormalizedtoespeciallyfortwo-phasesystems.Geometriccharacterizationofsamplevolumesforthepurposesofnanophaseanalysesusingconstituentphasesisoftendifficultforthree-phasesystemsneutron-scatteringdatadescribedbelow.Theconversionswerebecauseoftheusuallyunknownformsofthescatteringfactormadebyconsideringthevolumesofporeandmatrixphasescrossterms.Carefullydesignedneutron-scatteringexperimentscontainedin1gofsubstrate.Thedensitiesofthesilica(SBAwithcontrastvariationcan,however,measuretheindividual27andCPG)andcarbon(DMC)matrixphasesweremeasuredformfactorsofsuitablemultiphasesystems.Analysisofthe24,25bySANSandhigh-pressureheliumpycnometry.Thescatteringinvariantsofthree-phasesamplesyieldsgeometry-matrixdensitiesoftheamorphousCPGandSBAsilicaare2.2independentinformationaboutthephysicalpropertiesoftheg/cm3.ThemassdensityofDMCcarbonisalso2.2g/cm3,constituentphases(composition,massdensity,volume).Forindicatinggraphiticcarbon.ForSBA,theporevolumeis0.75polymersconfinedinsidenanopores,theformfactorisusuallycm3/g,andthedensityofthesilicaphaseis2.2g/cm3.unknown,makinganalysisofSANSdataviastructuralmodels4624https://doi.org/10.1021/acs.langmuir.1c00305Langmuir2021,37,4622−4631

3Langmuirpubs.acs.org/LangmuirArticleFigure2.Normalizedandbackground-subtractedSANScurvesforallthreesubstratesandthreedifferentd-PEIfillingsatthelowestandhighestexperimentaltemperatures.difficult.Thescatteringinvariantsdonotrequireany10−6Å−2forCPGandSBAand7.33×10−6Å−2forDMCassumptionsaboutthemorphologiesofnanodispersedphases(illustratedinFigure3).Theincoherentscatteringcontribu-andarereadilycalculatedfromthescatteringcurvesasthetions,whichareverylowforallsubstrates,weresubtractedintegralofthenormalizedscatteringintensitytimesthesquarefromthescatteringdata.InvariantcontributionsfromofthemomentumtransferasafunctionofthemomentumunmeasuredregionsatlowQwereapproximatedbyfittingtransfer(eq1).Equationsthatrelatetheinvariantsoftwo-andandintegratingGuinierfunctions,whilethoseathighQwerethree-phasenanodispersedsystemstothevolumefractionsandapproximatedbyfittingandintegratingPorodfunctions.Thosescatteringcontrastsoftheconstituentphasesareutilizedtocalculatedinvariantcontributionswereaddedtothe28extractthedensityandvolumeofthepolymerphases.experimentalinvariants.TheobtainedtotalinvariantsfortheSANS:PorousSubstrates.WeconsiderthemesoporousthreesubstratesatdifferentPEIloadingsandtemperaturesarematrixasphase1,andtheporespacesinthematrixasphase2.summarizedinFigure4andwillbediscussedbelow.SANS-ThescatteringinvariantsZzoftheempty(unfilled)supportsderivedporosities,showninFigure6astheporositiesforzeroarecalculatedfromthenormalizedintensityI(Q)andd-PEIloadings,showexcellentagreementwiththoseobtainedmomentumtransferQ,describedbythetwo-phaseinvariantfromtheliquidN2characterization.formulaScatteringcurvesforDMC-PEIandCPG-PEIsamplesat∞twotemperaturesaresummarizedinFigure2.StrongZ∫QIQQ22()d2(1)(*−*)2z==πϕ11−ϕρ12ρ(1)modulationsofthescatteringcurvesupond-PEIaddition0werefound,showingthesensitivityofSANSforporePEI.Thewhereρ*1andρ*2aretheneutron-coherentscatteringlengthscatteringcurvesyieldinformationaboutthestructuresofthedensities(SLD)oftheporoussupportandthevoids,poresystems.ForCPG,abroadcorrelationpeakcenteredaroundQ=0.03Å−1isfound,resultingfromthequasi-periodicrespectively,andϕ1isthevolumefractionofthesolid.TheNρjNAarrangementofporeswithlocalcylindricalgeometries.TheSLDofphasejiscalculatedasρj*=∑i=1biM,wherebiistheporesinSBAandCPGhavelocalcylindricalgeometries.Poresjcoherentscatteringlengthofatomi,NisthetotalnumberofinDMCarerandomlyshapedanddisordered,givingrisetoatomsinphasej,biistheatomicboundcoherentcrosssectionsDebye−Bueche-typescattering(Figure2).ofatomi,ρjisthemassdensity,Mjthemolarmass,andNA=CharacterizationofPore-ConfinedPEI.Onegoalofthis6.023×1023mol−1istheAvogadroconstant.Skeletonstudywastomeasurethedensityvolumesofnanodisperseddensitiesof2.2g/cm3areusedtocalculateSLDsof3.47×PEIphasesindifferentporeenvironments.Theneutron4625https://doi.org/10.1021/acs.langmuir.1c00305Langmuir2021,37,4622−4631

4Langmuirpubs.acs.org/LangmuirArticlecoherentSLDincreaseslinearlywithmassdensityandaffectsthescatteringcontrastsbetweenthenanodispersedphasesviaquadraticrelationships.InFigure3,theSLDvaluesarevisualizedfortheporoussubstratesandd-PEIatseveralhypotheticalmassdensities.Figure4.ScatteringinvariantsforthepureandPEI-impregnatedFigure3.VisualizationoftheneutroncoherentSLDsofthemesoporoussubstratesasfunctionsofPEIloadingandtemperature.nanodispersedphasespresentinthesamples.Theexperimentaluncertaintiesareindicatedbytheerrorbars.222SANSscatteringintensityofasampleiscontrolledbytheZ=[2()()πϕϕρ*−ρ*+ϕϕρ*−ρ*12122323scatteringcontrastsbetweenthedifferentphasespresentinthe2+ϕϕρ()*−ρ*](2)sampleandthevolumefractionsofthesephases(seeeq1).1313Forthepuresubstrates,thescatteringcontrastisgeneratedbytheporesembeddedinthesilicaorcarbonmatrices.TheInthisequation,thequantitiesϕ2,ϕ3,andρ*3areunknownadditionofd-PEItonanoporoussilicaleadstofillingofaforoursamples,whileϕ1andρ*1areknownfromthefractionoftheporespacewithpolymerandtheintroductionofcharacterizationoftheporousmaterials.Tosolvethisproblem,twoadditionalcontrasts(PEI-voidsandPEI-substrate).asetofthreeindependentequationsisneeded.Equation2isScatteringintensitiesareverysensitivetoscatteringcontrasts,constrainedbythenormalizationofvolumefractions:ϕ1+ϕ2whichareproportionaltothesquaresofthedifferenceinSLD+ϕ3=1.Thethirdrelationweintroduceutilizestheinverse(seeFigure3).Whilethescatteringcontrastbetweensilicaandrelationshipbetweenthemeandensityandthevolumeofthevoidsissimilartothatbetweensilicaandd-PEIatbulkdensity,porePEIphaseasfollows.Theh-PEIbulkdensityat20°Cisthecontrastbetweenbulk-densityd-PEIandvoidsisstronger1.03g/cm3.H/Disotopesubstitutionassumingidenticalmolarbyafactorofca.5.Therefore,increasesinthescatteringvolumesleadstoacalculatedd-PEIdensityof1.15g/cm3.Theinvariantareexpecteduponadditionofd-PEItosilicasamples.SLDford-PEIatamassdensityof1.15g/cm3isρ*=8.07×NIndeed,wefindthatthescatteringfromsilica-basedsamples10−6Å−2.ThevolumeofPEI(ϕ)isrelatedtotheporePEI3increaseswithincreasingPEIloading.Forthecarbonsubstrateρ*SLDthroughϕϕ=N.Usingthissetofequations,volume(DMC),thecontrastsituationisdifferent:carbonandd-PEIat3Nρ*3bulkdensityhavesimilarSLDsandcontrastsversusvoids,andfractionsandmassdensitiesofpore-confinedPEIweretheporosityofDMCisca.50%.ThevolumefractionofcarboncalculatedusingMathematica.isca.50%,andanapparentincreaseinthatvolumefractionPorePEIDensities.ThecalculatedPEIporedensitiesforthroughadditionofbulkd-PEIwoulddecreasethetermϕ1(1differentsubstrates,fillingdegrees,andtemperaturesare−ϕ1)ineq1.Therefore,theadditionofd-PEIatbulkdensitysummarizedinFigure5.Poredensificationwasfoundforwoulddecreasethescatteringinvariant.Importantly,wePEIinDMCcarbonnanopores,withPEIporedensitiesmuchobservedinsteadpronouncedincreasesinscatteringintensity3higherthanthebulkvalue(1.15g/cm)forallporefillingsandwithPEIaddition(seeFigure4).ThisfindingisastrongindicationthattheporePEIdensityintheDMCsampleissignificantlylargerthanitsbulkdensity,therebygeneratingadditionalcontrastbetweenPEIandvoidphases.AlthoughallthreesubstratesshowstrongincreasesinforwardscatteringwithincreasingPEIcontentsofthesamples,weneedtoconsidertheseincreasesinthecontextofnanodispersedthree-phasesystemswheretheSLDsandvolumefractionsofthephaseshavemorecompleximpactsonthescatteringintensitiesthanintwo-phasesystems.WewillnowquantifythedensificationofPEIinnanoporesfromSANSdata.Considerathree-phasesystemconsistingof(1)poroussupport,(2)unfilledpores(voids),and(3)aportionoftheporesthatisfilledwithPEI,withvolumefractionsofϕ1,ϕ2,andϕ3,respectively.TheinvariantformulaFigure5.MeanporedensitiesofPEIinsidenanoporesofthethree29forsuchathree-phasesystemreadssubstratesfordifferentfillingdegreesandtemperatures.4626https://doi.org/10.1021/acs.langmuir.1c00305Langmuir2021,37,4622−4631

5Langmuirpubs.acs.org/LangmuirArticleFigure6.CharacterizationofPEI-filledmaterials:liquidnitrogenmeasurementsofmeso-andmicroporevolumes(filledsquaresandcircles),PEIcontentsandPEIdistributionsintofilmsandplugfromSANS(opensymbols),andinaccessibleporefractionsfromthecombinedanalysisofN2andSANSdata(filledsymbols).Fromtoptobottom:SBAsilica,CPGsilica,andDMCcarbon.temperatures.ThestrongestdensificationisfoundinDMCCombinedSANSandLiquidN2SorptionAnalysis.poresatthelowestPEIloading,andporedensificationisCombinationoftheresultsfromliquidN2sorptionmeasure-somewhatreducedathigherPEIloading.ThisbehaviormentsandSANSyieldsfurtherinsightsintothenanometerindicatesstrongattractiveinteractionsbetweenthecarbonconfigurationofpore-confinedPEI,whichmayexisteitherasaporesurfacesandPEImoleculesatalowfillingdegree,wherelayerattheporewallsorasplugsoracombinationofboth.allmoleculesareindirectcontactwiththecarbonsurfaces.FromSANS,weobtaininformationabouttheaveragemassAdditionalPEImoleculesbeyondmonolayercoveragedensitiesofpored-PEIasfunctionsofthesubstrateandfillingexperiencereducedinteractionswiththesubstrateandcandegree.Analysisoftheliquidnitrogensorptiondata,thereforebeexpectedtoshowmorebulk-likeproperties.ThesummarizedinTable1,yieldsinformationaboutthethicknesslowestporefillingshowstheweaktemperaturedependenceofandvolumeofthesorptionlayerformedattheporewalls.porePEIdensity,whileatthehighestPEIloading,amoreLiquidN2measurementderivedporediametersdecreasecontinuouslywithincreasingPEIfillingoftheporesforallpronounceddecreaseofporePEIdensitieswithincreasingsubstrates,indicatingadsorbedlayerformation.temperatureisobserved.Usingasimplecylindricalmodel,theamountsofPEIForthetwosilicasubstrates,thePEIporedensitiesarelowercontainedinthesorptionlayersformedattheporewallscanthanthebulkdensityatthelowestPEIfillingandthenincreasebeestimatedfromthesedecreasesinporesizes.CylindricalwithincreasingPEIloading.Thisbehavior,whichismarkedlyshapesdescribeporegeometriesofSBAandCPG-10poresdifferentfromthebehaviorfoundforporePEIinDMCquiteaccuratelybutmaybelessaccurateforDMCnanoporescarbon,indicatesthatPEI-silicainteractionsarenotaswhicharemoreirregularlyshaped.IncorporationofPEIintoattractiveasPEI-carboninteractions.ThelowestPEIporeanadsorbedlayerleadstoreductionsinporevolumeanddensityisfoundforSBAsubstrateandlowloading.Inthisradius,rr,withrr=rp−t,whererpistheemptysubstratesample,alargefraction(uptoca.50%)ofthePEIappearstomesoporeradiusandtthethicknessofthesorptionlayer.Theoccupymicropores(seemicroporevolumesinTable1).Wevolumeofthisadsorbedlayer,V,isgivenbyV=πh(r2−filmfilmpbasethisassessmentonthreeobservations:(i)thereductioninr2).rmicroporesasmeasuredbyliquidN2BET,(ii)thereductionTheemptysubstratemesoporevolumes(Vp),summarizedinsmall-anglescatteringathighQforsamplescontainingPEI,inTable1,arereduceduponPEIadditionduetothevolumesand(iii)themeasuredvolumeanddensityofthePEIfilmastakenupbyPEIinfilmsandplugs.ThevolumeofPEIineachobtainedfromthecombinedliquidN2andSANSanalysissample,VPEI,isobtainedfromthequotientofPEImassper(showninFigure6anddiscussedlaterinthispaper).PEIporesamplevolumeandtherespectivePEIdensitymeasuredbydensityatthehighestPEIloadingishigherinSBAporesthanSANS.TheaccessibleporevolumeVrcanfurtherbereducedinCPG-10pores.TheporediameterofSBA-15ismuchbyexcludedporevolumeinaccessibletoliquidnitrogen,Ve,smallerthantheporediameterofCPG-10.leadingtoVr=Vp−Vfilm−Vplugs−Ve.ThequantitiesVpand4627https://doi.org/10.1021/acs.langmuir.1c00305Langmuir2021,37,4622−4631

6Langmuirpubs.acs.org/LangmuirArticleFigure7.Bead-springmodelofthebranchedpolymerrepresentingPEI(a).Thegold,magenta,andcyanbeadsrepresentprimary,secondary,andtertiaryamines,respectively.AcylindricalporeimpregnatedwithPEIataloadingdensityofρmon(ρmon=numberofPEIbeads/volumeofcylinder)showingredattractivebeadsandgreenrepulsivesupportbeads(b).RadialdensitydistributionofPEIbeadsρ(r),wherer=0σisthecenterofthepore,σisthebeaddiameter,andρmaxisthemaximumdensityinthevicinityoftheporewall(c).Figure8.DependenceofρonTfordifferentvaluesofρandε.Filledcircles:ρ=0.05σ−3,opencircles:ρ=0.1σ−3,filledsquares:ρmaxmonwmonmonmon=0.2σ−3,opensquares:ρ=0.3σ−3,andfilledtriangles:ρ=0.4σ−3.monmonVraremeasuredintheliquidnitrogenexperimentsofpristineaggregatingtominimizesurfacearea),polymer-to-substrateandPEI-filledsamples,respectively.Thevolumeofplugsisinteraction(asmanifestedinthedifferentchemistriesofthecalculatedfromthetotalvolumeofPEI(VPEI)throughVplugs=pore,wherenanoporouscarbonhasthehighestattractiveVPEI−Vfilm.AsthismodelassumesthatallPEIisineitherfilminteractionswithPEI),andtemperatureonplugformationandorplugs,anyadditionalreductioninporevolumemeasuredbythedensificationofPEIonporesurfaces.Weusedthecoarse-liquidnitrogenbeyondthevolumetakenupbyPEIisassignedgrainedmodelandmoleculardynamics(MD)simulationtoporeblockagecausedbyPEIplugs.protocoldescribedinrefs11and19whereabead-springInFigure6,thedistributionsofPEIbetweenfilmsandplugsmodelofabranchedpolymerisimpregnatedintoaporousareshownforthedifferentfillingdegreesofthethreedifferentsubstrate(seeFigure7).Inthiscase,weconsideredasubstrates.Atlowloadings,porePEIexclusivelyformsfilmsatcylindricalporesimilartothosefoundinSBA-15.Inthetheporewalls.IntheSBAandDMCsamples,themicroporessimulations,thebranchedpolymerrepresentingPEIhasfillwithPEIatlowloading,indicatedbythedisappearanceofprimary,secondary,andtertiaryaminebeads.TheattractivemicroporosityintheN2sorptionmeasurements.WhileitisinteractionbetweenthesubstratewiththeprimaryaminesinalsopossiblethatthePEIonlyclogsthemicroporethroatsandPEIiscontrolledbytheLennard−Jonesinteractionparameter,doesnotfillmicropores,theobservedreductionsinscatteringεw,whereahighervalueofεwmeansanincreaseintheintensityatlargeQaremoreconsistentwithmicroporefilling.attractionbetweenwallbeadsandprimaryamines.SurfaceAtthehighestloadings,plugsforminallsamples.Theseplugsenergyistheenergyneededtomaintainorcreateasurface,areinadditiontothePEIfilmsattheporewalls,whichstillandinthiscase,attractiveinteractionsbetweenpolymerbeads,containthemajorityofPEI.Noorveryminorcloggingofporesetatε=1/3kBTwherekBTisthermalenergy,isusedtospacesisobservedintheCPGsamples,whichfeaturethecreatevacuum-to-polymerandsubstrate-to-polymerinterfaces.largestpores.However,porecloggingoccursandismoreCanonicalorNVTensembleMDsimulationswereperformedpronouncedathigherPEIloadingsforthetwosubstrateswithfordifferentpolymerloadings,ρmon,whereaLangevinthesmallerpores(SBAandDMC).thermostatcontrolsthetemperature.Ourprevioussimulation1920,21MDModeling:PorePEIProperties.WeinvestigatedtheresultsagreewiththeneutronscatteringresultsinSBA-interplaybetweensurfaceenergy(asmanifestedbythePEI15,wheretheimpregnatedPEIfillstheporewallbeginningat4628https://doi.org/10.1021/acs.langmuir.1c00305Langmuir2021,37,4622−4631

7Langmuirpubs.acs.org/LangmuirArticletheporewallsandgrowsconcentricallybutnon-uniformly,atlowloadingisbelowornearitsbulkdensity,andporePEItherebysuggestingthatatacertainpolymerloading,plugsanddensificationincreaseswithincreasingtheporefilling.voidsinsidethecylindricalporesareformed.ForthecaseofThePEIporedensitiesatthehighestloadingstakevaluesofoursimulations,theplugsandvoidsareobservedataloadingca.1.4g/cm3inSBAandca.1.6g/cm3inDMCsubstrates,ofρ=0.2to0.4σ−3atatemperatureofT=1T*.Tisthewhichhavesimilarporeradiiof2.77and3.0nm,respectively.montemperatureinreducedunits(atypicalconventionforcoarse-CPG-10hassignificantlylargerporeswitharadiusofca.6.7grainedMDsimulations).Forthispaper,weperformednm.BecausetheporePEIdensitiesarelargelycontrolledbysimulationatdifferentT*toseethetrendofporepluggingasasubstrate−polymerinteractionsatlowerPEIloadings,thefunctionofT.Weexpecttoseeashiftinthepluggingbehaviorsubstratechemistriescontrolthebehavior:forweaklyattractiveasseeninthelocalradialdensity,ρ(r),asafunctionofεw,T,silica,PEIdensityincreaseswithfilling,whileforstronglyandρmon.attractivecarbon,itdecreaseswithfilling.CarbonmayinteractToquantifythedensificationofPEInearporesurfaces,wewithPEIasanelectronacceptor,givingrisetostrong30measurethemaximumdensity,ρmax,ofPEIinthevicinityofdensification.Thiseffectisexpectedtobemostpronouncedtheporewall.Weobservethatifεwislow(2kBT),ρmaxatlowPEIloadingwhenthemajorityofPEIisindirectdecreaseslinearlywithtemperature(seeFigure8a).ForhighercontactwiththeDMCporesurfaces.Theimpactsofsubstrate-valuesofεw(see4and8kBTinFigure8b,c),ρmaxremainsPEIinteractionsarereducedatthehighestloadingwheretherelativelyconstantforlowloading(lowvalueofρmon),whilefractionofpolymermoleculesincontactwiththesubstrateisρmaxdecreaseslinearlywithTforhighervaluesofρmon.Sincesmaller.Inthissituation,poreconfinementmayalsoleadtotheplotsofρmaxversusThaslineardependence,wecanfitthechangesinthephysicalpropertiesoftheporefluid.PEIplugsdatapointswithalinearequation,ρmax(T)=mmaxT+b,whereorbubblesintheporesexperiencecompressiveforcescausedmmaxandbaretheslopeandy-interceptofthelinearequation,bytheLaplacepressure,whichforspheresisgivenbyΔP=respectively(seeFigure9).Forthelowestvalueofεw,thereis2γ/R,withRbeingthedropletradiusandγthesurfacetension.PEIsurfacetensioncanbeestimatedusingtheempirical312parachormodel,whichgivesavalueofca.53mJ/m.GiventhesimilarsizesofDMCandSBApores,similarvaluesoftheLaplacepressuresshouldoccurinbothsamples.PEIdroplet(plug)pressuresofca.350bararecalculatedfora3nmradius(DMC,SBA)and160barfora6.7nmradius(CPG).TheporePEIdensificationabovethebulkvalueinSBAathighPEIloadingsmaythereforebecausedbysurfacetensioneffects.Inbothsilicasamples,theCCvaluesshownotemperaturedependenceatthehighestPEIloading,whileatthelowerloading,theCCvaluesarereducedatahighertemperature.Thecaptureactivitypernitrogenatomisca.50%ofthetheoreticalmaximumforthetwosilicasamplesatthehigherloadings.However,theCCvaluesofDMC/PEIarestronglysuppressedatthehighertemperature.ThiseffectcouldbeFigure9.Dependenceofmmaxonρmonfordifferentvaluesofεw.causedbythecombinationofstronglyattractiveinteractionsbetweentheporewallsandPEIandincreasedconfigurationalnon-monotonicdependenceofmmaxwithrespecttoρmon,andflexibilityofPEImoleculesathightemperature,leadingtothetransitionoccurswhenpolymerbeadsbegintooccupytheincreasedporewall-PEIcontactandthereforeareductioninmiddleregionofthepore,suggestingtheformationofplugs.PEIsorptionsitesforCO2.ThisadsorptionbehaviorishighlyFurthermore,mmaxisinvariantwithρmonwhenwall-to-primarydesirableforCO2captureinTSAsystems.amineinteraction,εw,isstrong,suggestingthatatlowρmon,theTheMDmodelingreproducesseveralimportantfeaturesofpolymercoatstheporesurface,ρmaxisinvariantwithT,andtheexperimentalpore-confinedPEI.DensificationofporePEIplugsarenotformed.OursimulationimpliesthatincreasingεwwithdecreasingtemperatureisobservedinDMCcarbonshiftsthetransitioninthelocationofρmonwhenbeadsbegintosubstrates,especiallyatlowpolymerloading.Furthermore,occupythemiddleregion,whichdecreasestheprobabilityofplugformationismostpronouncedinthetwosilicasamplesplugformation.withweakpolymer−substrateinteractions,whiletheamountofpolymerinplugsissignificantlyreducedforDMCcarbon■DISCUSSIONsubstrate.ThisbehaviorisreproducedintheMD,whereThroughthecombinationofSANSexperimentswithotherdecreasingplugformationisfoundinporeswithstronglyexperimentalcharacterizationandMDmodeling,wehaveattractivesubstrate−polymerinteractions.ThePEI−carboncharacterizedthephysicalpropertiesofPEIconfinedininteractionsaremuchmorestronglyattractivethanthePEI−nanoporesofdifferentchemicalidentitiesandporestructures.silicainteractions,whichareonlyweaklyattractive,thatis,TheresultsshowthatPEIentersthenanopores,whereitlesserthanequallyattractivecomparedtopolymer−polymerresidesinananodispersedform.Liquidnitrogensorptioninteractions.showsthatPEIfilmsformattheporewalls.FromSANS,densitymeasurementsofporePEIwerecarriedoutby■CONCLUSIONSanalyzingthescatteringinvariantsandutilizingformulasforWehavemeasuredthedensitiesofnanopore-confinedPEIinscatteringfromthree-phasesystems.ForPEIincarbonpores,asilicaandcarbonnanoporesusingSANS.WefoundthatPEIinstrongdensificationeffectwasfound,whichwasmostcarbonnanoporesissignificantlydenserthanbulkPEI,whilepronouncedatthelowloadings.ForPEIinsilicapores,PEIsilicananopore-confinedPEIhadapproximatelybulkdensity.4629https://doi.org/10.1021/acs.langmuir.1c00305Langmuir2021,37,4622−4631

8Langmuirpubs.acs.org/LangmuirArticleFromthecombinedanalysisofSANSinvariantsandliquidJan-MichaelCarrillo−CenterforNanophaseMaterialsnitrogensorption,thedistributionofporePEIbetweenlayersSciences,OakRidgeNationalLaboratory,OakRidge,ontheporewallsandplugswasextracted.TheamountofPEITennessee37831,UnitedStates;orcid.org/0000-0001-inplugsislargerinthesilicaporescomparedtothenanopores,8774-697XandthisbehaviorwasreproducedinMDsimulationsthroughBobbyG.Sumpter−CenterforNanophaseMaterialsvariationofthepolymer−substrateinteractions.OurresultsSciences,OakRidgeNationalLaboratory,OakRidge,obtainedforthesampleswithSBAsubstratesconfirmthemainTennessee37831,UnitedStates;orcid.org/0000-0001-conclusionsofanearlierSANSstudyonthatsystem(ref16).6341-0355Inthatstudy,formfactormodelingofthenanoporoussilica−Completecontactinformationisavailableat:polymerhybridsamplewasperformed.Fromthatanalysis,thehttps://pubs.acs.org/10.1021/acs.langmuir.1c00305authorsconcludedthatthefirst20%volofporePEIformscoatingsontheporewalls,andadditionalPEIisstoredinplugsAuthorContributionsintheporespaces.Thisfindingiscorroboratedbyourstudy,Themanuscriptwaswrittenthroughthecontributionsofallwheretheonsetofplugformationisfoundatsimilarvaluesofauthors.AllauthorshavegivenapprovaltothefinalversionofPEIporefilling.Theauthorsofref16notethatblockingofthemanuscript.poreregionsoccursathigherloadingsofPEIintothenanoporespaces,whichmightrenderfractionsoftheporePEINotesinaccessibleforCO2capture.WecanconfirmandquantifythisTheauthorsdeclarenocompetingfinancialinterest.effectwhichtakesplaceinthenarrowporeSBAsilicabutnotinthewiderporesofCPGmaterial.CPG-typematerialsmight■beadvantageoussubstratesforthesehybridmaterialsbecauseACKNOWLEDGMENTStheirsponge-likeporenetworksaremoreinterconnectedWethankChristopherW.JonesandMatthewE.PotteratcomparedtotheMCM/SBA-typearrangementsofparallelGeorgiaTechUniversityforprovidingthedeuteratedsingleporeswherecoincidentalcloggingofbothporethroatspolymers,impregnationofthesupports,CO2capturemeasure-mightdeactivatetheentireporewithalengthofuptoseveralments,TGAandliquidN2measurements,andstimulatingmicrons.TheDMCcarbonmaterials,whichhavesimilarporediscussions.ThisresearchwassupportedaspartofUNCAGE-sizestoSBA,donotsufferfromsignificantpore-blockingME,anEnergyFrontierResearchCenterfundedbytheU.S.effects,whichmaybeduetobothmoreattractivecarbon-PEIDepartmentofEnergy,OfficeofScience,BasicEnergyinteractionsfavoringfilmformationandthemoreintercon-Sciences,underaward#DE-SC0012577,andtheCenterfornectedporenetworkstructuresofDMC.FromapracticalNanophaseMaterialsSciences,whichareUSDepartmentofperspective,DMCcarbonofferstheadditionaladvantagesofEnergyOfficeofScienceUserFacilities.ThisresearchusedstrongchemicalstabilityagainstwatervaporandexcellentCOresourcesattheSpallationNeutronSource,aDOEOfficeof2sorptionpropertiesforTSAapplications.ScienceUserFacilityoperatedbytheOakRidgeNationalLaboratory.ThismanuscriptwasauthoredbyUT-Battelle,■LLCundercontractno.DE-AC05-00OR22725withtheU.S.ASSOCIATEDCONTENTDepartmentofEnergy.TheUnitedStatesGovernmentretains*sıSupportingInformationandthepublisher,byacceptingthearticleforpublication,TheSupportingInformationisavailablefreeofchargeatacknowledgesthattheUnitedStatesGovernmentretainsahttps://pubs.acs.org/doi/10.1021/acs.langmuir.1c00305.non-exclusive,paid-up,irrevocable,world-widelicensetoDSCmeasurementsandN2adsorption−desorptionpublishorreproducethepublishedformofthismanuscript,isothermsat77Kofallsamples(PDF)orallowotherstodoso,forUnitedStatesGovernmentpurposes.TheDepartmentofEnergywillprovidepublicaccess■totheseresultsoffederallysponsoredresearchinaccordanceAUTHORINFORMATIONwiththeDOEPublicAccessPlan(http://energy.gov/CorrespondingAuthordownloads/doe-public-access-plan).GernotRother−ChemicalSciencesDivision,OakRidgeNationalLaboratory,OakRidge,Tennessee37831,United■States;orcid.org/0000-0003-4921-6294;ABBREVIATIONS2-COLEmail:rotherg@ornl.govCCcapturecapacitySANSsmall-angleneutronscatteringAuthorsUmaTumuluri−ChemicalSciencesDivision,OakRidgeNationalLaboratory,OakRidge,Tennessee37831,United■REFERENCESStates(1)Rubin,E.S.;Mantripragada,H.;Marks,A.;Versteeg,P.;Kitchin,KuanHuang−DepartmentofChemistry,UniversityofJ.Theoutlookforimprovedcarboncapturetechnology.Prog.EnergyTennessee,Knoxville,Tennessee37996,UnitedStatesCombust.Sci.2012,38,630−671.WilliamT.Heller−SpallationNeutronSource,OakRidge(2)Pires,J.C.M.;Martins,F.G.;Alvim-Ferraz,M.C.M.;Simoes,NationalLaboratory,OakRidge,Tennessee37831,UnitedM.Recentdevelopmentsoncarboncaptureandstorage:Anoverview.Chem.Eng.Res.Des.2011,89,1446−1460.States;orcid.org/0000-0001-6456-2975(3)Kenarsari,S.D.;Yang,D.;Jiang,G.;Zhang,S.;Wang,J.;Russell,ShengDai−ChemicalSciencesDivision,OakRidgeNationalA.G.;Wei,Q.;Fan,M.ReviewofrecentadvancesincarbondioxideLaboratory,OakRidge,Tennessee37831,UnitedStates;separationandcapture.RSCAdv.2013,3,22739−22773.DepartmentofChemistry,UniversityofTennessee,Knoxville,(4)Samanta,A.;Zhao,A.;Shimizu,G.K.H.;Sarkar,P.;Gupta,R.Tennessee37996,UnitedStates;orcid.org/0000-0002-Post-Co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