SupplementaryInformationfor:Plasticization-resistantNi2(dobdc)/polyimidecompositemembranesforCO2removalfromnaturalgas

JonathanE.Bachman1andJeffreyR.Long1,2,3*

1DepartmentofChemicalandBiomolecularEngineering,2DepartmentofChemistry,UniversityofCalifornia,Berkeley,California,94720,USA,3MaterialsSciencesDivision,LawrenceBerkeleyNationalLaboratory,Berkeley,California,94720,USA.

Electronic Supplementary Material (ESI) for Energy & Environmental Science.This journal is © The Royal Society of Chemistry 2016

Methods

SynthesisofNi2(dobdc)nanocrystals

Solid2,5-dihydroxyterephthalicacid(1.0g,5.0mmol;H4(dobdc))and16mmolofNi(NO3)2·6H2O

wereaddedtoamixtureof400mLofDMF,27mLofethanol,and27mLofwaterina500-mL

round bottom flask. 5 mL of triethylamine was added rapidly while stirring under an N2

atmosphere. The Ni2(dobdc) nanocrystals precipitated within minutes, but was allowed to

continue for 2 hours. The dispersed Ni2(dobdc) nanoparticles were immediately collected by

centrifugation,thesolidwasredispersedin250mLofDMF,andthesuspensionwasheatedat

120°Cfor6h.TheNi2(dobdc)undergoesacolorchangefromgreentobrownuponheating.The

centrifugationandDMFwashingstepswererepeatedfivetimesinordertoremoveunreacted

ligand. The nanocrystals were then collected by centrifugation and redispersed in 250mL of

methanolandthesuspensionwasheatedat60°C for2-5h.Thecentrifugationandmethanol

washing steps were repeated six times in order to exchange all of the DMF for methanol,

includingthosemoleculescoordinatedtothemetalsites.FullremovalofDMFwasconfirmedby

infraredspectroscopy.Nanocrystalswere thenstored inmethanoluntilmembranecasting,or

driedunderreducedpressureat180°Cfor24hpriortogasadsorptionmeasurements.

PolymerSynthesis

6FDA-DAT, 6FDA-DAM, and 6FDA-durene were formed from 2,2'-bis-(3,4-dicarboxyphenyl)

hexafluoropropanedianhydride(6FDA)andeither2,4,6-trimethyl-1,3-phenylenediamine(DAM),

2,6-diaminotoluene(DAT)or2,3,5,6-tetramethyl-1,4-phenylenediamine(durene)usingstandard

chemicalimidizationtechniques.1,2Therandom1:1copolymer6FDA-DAT:DAMwassynthesized

in a similar manner, according to reported techniques.3The dianhydride and diamines were

purchasedfromTCI.Beforeuse,6FDAwaspurifiedoncebyvacuumsublimation,DAMandDAT

werepurifiedthreetimesbyvacuumsublimation,anddurenewaspurifiedbyrecrystallization

in methanol. N-methyl-2-pyrrolidone (NMP) was purchased from Spectrum Chemicals and

vacuumdistilled immediately beforeuse. Triethylamine and acetic anhydridewerepurchased

fromEMDandSigma-Aldrich, respectively,andwereusedas received.Adryatmospherewas

maintainedwithinthereactionglasswarebyflowinghousenitrogenthroughaDrieritecolumn

(W.A.HammondDrieriteCo.,Ltd.,Xenia,OH)upstreamofthereactionvessel.Allglasswarewas

attachedtoflowing,drynitrogenafterbeingflamedried.CelluloseacetateandMatrimid®were

kindlyprovidedbyMembraneTechnologyandResearch(MTR)Inc.

Membranecastingandactivation

Concentration ofNi2(dobdc) inmethanolwere determined by sonicating a stock solution and

reducing a 1-mL aliquot to dryness to find the mass of activated nanocrystals, and resulting

stock solutionswere found tobe~30mg/ml. For compositemembranes, analiquot from the

Ni2(dobdc)stocksolutioninmethanolwastakenandredispersedin10mLofthecastingsolvent

ina20mLvial.TheNi2(dobdc)wasthencentrifugedandredispersedin10mLofcastingsolvent

in order to ensure no residual methanol was present during membrane casting.

Dichloromethanewasusedasthecastingsolventforallpolymersexceptcelluloseacetate,for

whichacetonewasused.Thenanocrystalsuspensionwasthensonicatedusingahornsonicator

for 1minwith addition of casting solvent in order tomaintain a total volume of 10mL. The

polymerwasthendissolved intotheNi2(dobdc)suspensionandthemixturewassonicatedfor

another 1 min. The mixture was cast onto a glass plate and the solvent was allowed to

evaporateover thecourseof~24h,andtheresulting filmswere foundtobe40-70μmthick.

The freestanding filmwas thendried inavacuumovenat120°C for24h inorder to remove

residualcastingsolvent.

The loading of Ni2(dobdc) nanocrystals in the composite film was determined by a

thermogravimetric analysismethod. For reference, theNi2(dobdc) powderwas first activated

underflowingN2at180°Cfor1.5htoensureactivation,andthenthesampleswereheatedto

600°CunderflowingO2.Theremainingoxidemasswascomparedtotheinitialactivatedmass

ofthemetal-organicframework.ThesameprocedurewasconductedfortheNi2(dobdc)/6FDA-

DAMfilms.Thepercentageofmassremainingaftertherampto600°CunderO2isattributable

to metal oxide, and from this the amount of activated M2(dobdc) present in the film was

obtained.

Gaspermeabilitymeasurements

Singlecomponentgaspermeationexperimentswereconductedonan instrumentconstructed

in-house.Theprocedureformembranesamplepreparationisdescribedinourpreviouswork.4

Formulticomponentpermeationexperiments,anequimolarmixtureofCO2/CH4wassweptover

the feed side of themembrane at a rate > 100x the permeation rate, in order to ensure no

concentrationpolarization.Thecompositionofthepermeate,pCO2/(pCO2+pCH4),wasdetermined

bycollectingthepermeate,andthenexpandingittoamassspectrometer(MKSMicrovision2).

Themassfractionof (mass44)/[(mass44)+(mass15)] inthecollectedpermeatewasusedto

determine themixed-gas selectivity. A calibration of themass fractionwas determined using

standardswith10%,50%,and90%CO2inmethane.StandarderroroftheCO2/CH4molefraction

calibration is 0.79%. The uncertainty in the downstreammole ratio, aswell as uncertainty in

mixed-gasselectivities,isapropagationofuncertaintyfromthestandarderrorinthemoleratio

calibration.

Gasadsorptionmeasurements

Low-pressure gas adsorption data between 0 and 1.1 bar were measured using a high

throughput gas-adsorption analyzer constructed by Wildcat Discovery Technologies, using a

methoddescribedpreviously.5Samplesconsistingof50-100mgofNi2(dobdc)powder,polymer

film,ormixed-matrixfilmwereloadedintoapreweighed4mL,andheatedat180°Cfor24h.

Themassoftheactivatedsamplewasthenusedasthebasisfortheadsorptionmeasurements.

Afteranadsorptionisothermwasmeasured,thesamplewasreactivatedat180°Cfor6hbefore

measuringasubsequentadsorptionisotherm.

Determinationofglasstransitiontemperatures

The glass transition temperatures (Tg) were determined by differential scanning calorimetry

usingaTAQ200instrument.Temperaturescanswereconductedat10°C/minstartingat50˚C

andendingatatemperaturethatvarieddependingonthepolymer,whichwas~20˚Cabovethe

observedTg.Multipletemperaturecycleswererun,andthereportedTgwastakenfromeither

thesecondorthirdcycle.

Calculatingpermeability

In order to ensure steady-state permeation rates were attained, permeabilitymeasurements

wererunforatleast6×thetimelag,wherethetimelagisdefinedastheinterceptonthetime-

axisonthepressurevs.timeplotwherealineisdrawnfittingthelinearregion.6Thetimet=0

corresponds towhen the downstream volume is closed to vacuum and the gas is allowed to

beginaccumulating.Attheendof6×thetimelag,theslopeofthelinefittingthelast20%ofthe

datawasusedtodeterminethesteady-statepermeationrate.Inthecasethatthetimelagwas

not detectable, i.e., for CO2 permeation in Ni2(dobdc)/6FDA-durene, the permeation at each

pressurepointwasallowedtoproceedforthreeminutes.

Thepressure-basedpermeabilityiscalculatedusingEqn.1,wherePisthepermeability,listhe

thicknessofthefilm,Vcell isthevolumedownstreamofthemembranewheregasisallowedto

accumulateduringapermeationtest,Aistheareaofthemembraneexposedtopermeation,Pf

is the upstream pressure, R is the gas constant, T is the temperature in K, 𝑑𝑝 𝑑𝑡 !!is the

steady-statepermeationrate,and 𝑑𝑝 𝑑𝑡 !"#$istheleakrate.Wereportpermeabilitiesinthe

unitofBarrer(1Barrer=10!!! !"! !"# ∗!"

!"!∗!∗!"#$).

𝑃 = !∗!!"##!∗!!∗!∗!

𝑑𝑝𝑑𝑡 !!

− 𝑑𝑝 𝑑𝑡 !"#$ (1)

Uncertaintyinthepermeabilitywaspropagatedfromuncertaintyinthefilmthickness,filmarea,

upstreampressuretransducer,temperature,anddownstreamvolume.

GPC

Molecularweightsweredeterminedusing aViscotek TDA302 size exclusion chromatography

(SEC)systemcalibratedrelativetopolystyreneandusingtetrahydrofuran(THF)asthesolvent.

Supplementary Table 1 presents the weight-averaged molecular weight, number-averaged

molecularweight,andpolydispersityindexforthesamplesconsideredinthisstudy.

Figures

SupplementaryFigure1|PowderX-raydiffractionpatternforNi2(dobdc)nanocrystals.

Supplementary Figure 2 | Equilibriumadsorption isothermsofCO2 (green) andCH4 (black) inneatNi2(dobdc)at35˚C.Blacklinescorrespondtodual-siteandsingle-siteLangmuir-FreundlichfitsforCO2andCH4,respectively.

SupplementaryFigure3|CO2/CH4adsorptiveselectivitiesinneatNi2(dobdc)aspredictedfromIdealAdsorbedSolutionTheory(IAST),withadsorptiondatatakenat35˚Candcalculatedat1bartotalgaspressure.

Supplementary Figure 4 | Thermogravimetric analysis curve for the decomposition ofNi2(dobdc).From0-110minutes,thesamplewasactivatedat180˚CunderflowingN2,andthenwasheated to 600 ˚Cunder flowingO2. Thedifferencebetween the activatedmass and finalmasswasusedtocalculatetheloadingofNi2(dobdc)inthecompositefilms.

Supplementary Figure 5 |Thermogravimetric analysis curve for compositemembranes. FilmswerefirstactivatedunderflowingN2at180˚Candthenheatedto600˚CunderflowingO2.Thedifferenceinmassbetweentheactivatedfilmandremainingmetal-oxidewasusedtocalculatetheamountofNi2(dobdc)inthecomposite.

SupplementaryFigure6|CO2adsorptionisothermsintheneatpolymer(closedtriangles)andcomposite(closedcircles)membranes.OpencirclescorrespondtotheweightedaverageofCO2adsorbedbetweentheneatpolymerandNi2(dobdc)powder.Amountsadsorbedat1barwereused for thecalculationofpurecomponentsolubilityparameters,SCO2.

Supplementary Figure 7 | CO2 (circles) and CH4 (triangles) permeability data for neat (open) and composite(closed)membranesunderanequimolarfeedofCO2andCH4.UncertaintieswerepropagatedfromthestandarderrorinthecalibrationcurvewhichdeterminedtheCO2/CH4ratiointhepermeate.SupplementaryTable1|Sizeexlusionchromatographycharacterizationforeachpolymertested.MwandMnrefertoweightaverageandnumberaveragemolecularweight,respectively.PDIisthepolydispersityindex.

Polymer Mn Mw PDI6FDA-durene 7,300 24,800 3.36FDA-DAM 69,500 166,000 2.46FDA-DAT:DAM 74,200 129,400 1.76FDA-DAT 15,700 37,000 2.3Matrimid® 34,800 79,500 2.3Celluloseacetate 62,600 166,000 2.7

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