92ꢀ
SipingꢀJianꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ37ꢀ(2016)ꢀ91–97ꢀ
theꢀ reactionꢀ mixtureꢀ wasꢀ difficult.ꢀ Sun’sꢀ groupꢀ [14]ꢀ preparedꢀ
theꢀ sameꢀ Ni@Pdꢀ NPsꢀ byꢀ aꢀ one‐stepꢀ method,ꢀ andꢀ theseꢀ NPs,ꢀ
supportedꢀonꢀgraphene,ꢀexhibitedꢀhighꢀcatalyticꢀactivityꢀduringꢀ
Suzuki‐Miyauraꢀcross‐couplingꢀreactions.ꢀ
microscopyꢀ(TEM)ꢀmicrographsꢀofꢀtheꢀsamplesꢀwereꢀacquiredꢀ
usingꢀaꢀJEM‐2010HRꢀ(JEOL).ꢀ
2.2.ꢀ ꢀ SynthesisꢀofꢀNi@PdꢀNPsꢀ
Functionalizedꢀ anilinesꢀ areꢀimportantꢀintermediatesꢀinꢀtheꢀ
pharmaceutical,ꢀ chemical,ꢀ agrochemical,ꢀ andꢀ dyeꢀ industriesꢀ
2
Palladium(II)ꢀbromideꢀ(PdBr ,ꢀ26.6ꢀmg,ꢀ0.1ꢀmmol),ꢀnickel(II)ꢀ
[15].ꢀ Theꢀ traditionalꢀ non‐catalyticꢀ reductionꢀ ofꢀ nitroarenesꢀ
acetateꢀ tetrahydrateꢀ (Ni(ac) ∙4H
2
2
O,ꢀ 24.9ꢀ mg,ꢀ 0.1ꢀ mmol),ꢀ TOPꢀ
usingꢀ stoichiometricꢀ reducingꢀ reagentsꢀ suchꢀ asꢀ sodiumꢀ boro‐
hydride,ꢀsilanes,ꢀandꢀhydrazineꢀderivativesꢀoftenꢀcausesꢀseriousꢀ
environmentalꢀ problemsꢀ [16],ꢀ andꢀ soꢀ catalyticꢀ hydrogenationꢀ
withꢀ supportedꢀ metalꢀ catalystsꢀ hasꢀ capturedꢀ widespreadꢀ re‐
searchꢀ interestꢀ inꢀ recentꢀ yearsꢀ [17,18].ꢀ Underꢀ mildꢀ reactionꢀ
(0.5ꢀ mL),ꢀ andꢀ OAmꢀ (10.0ꢀ mL)ꢀ wereꢀ addedꢀ toꢀ aꢀ 25ꢀ mLꢀ Tef‐
lon‐lined,ꢀ stainlessꢀ steelꢀ autoclaveꢀ containedꢀ inꢀ aꢀ gloveboxꢀ
filledꢀ withꢀ nitrogenꢀ atꢀ roomꢀ temperature.ꢀ Thisꢀ mixtureꢀ wasꢀ
thenꢀheatedꢀatꢀ255ꢀ°Cꢀforꢀ2ꢀhꢀandꢀsubsequentlyꢀallowedꢀtoꢀcoolꢀ
slowlyꢀ toꢀ roomꢀ temperature.ꢀ Theꢀ NPꢀ productꢀ wasꢀ separatedꢀ
fromꢀ theꢀ reactionꢀ mixtureꢀ byꢀ addingꢀ 40ꢀ mLꢀ isopropanol,ꢀ
followedꢀbyꢀtwoꢀcentrifugationsꢀatꢀ10000ꢀrpmꢀforꢀ10ꢀmin.ꢀTheꢀ
NPsꢀ wereꢀ furtherꢀ purifiedꢀ andꢀ collectedꢀ byꢀ firstꢀ dispersingꢀ
themꢀinꢀanhydrousꢀn‐hexaneꢀ(5ꢀmL)ꢀthenꢀaddingꢀaꢀ1:1ꢀmixtureꢀ
ofꢀethanolꢀandꢀisopropanolꢀandꢀcentrifugingꢀatꢀ10000ꢀrpmꢀforꢀ
10ꢀ min.ꢀ Theꢀ resultingꢀ NPꢀ powderꢀ wasꢀ redispersedꢀ inꢀ anhy‐
drousꢀ n‐hexane.ꢀ Theꢀ preparedꢀ Ni@Pdꢀ core‐shellꢀ NPsꢀ hadꢀ aꢀ
Ni:Pdꢀ molarꢀ ratioꢀ ofꢀ approximatelyꢀ 1:1.ꢀ Underꢀ theꢀ sameꢀ
conditions,ꢀ heterogeneousꢀ nobleꢀ catalystsꢀ suchꢀ asꢀ Au/TiO
2
,ꢀ
Au/γ‐Al ,ꢀandꢀPd‐Pt‐carbonꢀnanotubesꢀ(CNTs)ꢀhaveꢀexhibit‐
2 3
O
edꢀhighlyꢀselectiveꢀreductionꢀofꢀnitroarenes.ꢀHowever,ꢀtheꢀma‐
jorityꢀofꢀtheseꢀtransformationsꢀwereꢀassociatedꢀwithꢀrelativelyꢀ
lowꢀ turnoverꢀ frequencyꢀ (TOF)ꢀ valuesꢀ thatꢀ wouldꢀ needꢀ toꢀ beꢀ
furtherꢀ improvedꢀ toꢀ realizeꢀ theꢀ practicalꢀ applicationsꢀ ofꢀ no‐
ble‐metalꢀcatalystsꢀ[19–21].ꢀ
Inꢀ theꢀ presentꢀ work,ꢀ Ni@Pdꢀ core‐shellꢀ NPsꢀ withꢀ differentꢀ
Ni/Pdꢀmolarꢀratiosꢀwereꢀsynthesizedꢀusingꢀaꢀsequentialꢀreduc‐
tionꢀ method.ꢀ Inꢀ thisꢀ process,ꢀ Niꢀ andꢀ Pdꢀ precursorsꢀ wereꢀ se‐
quentiallyꢀreducedꢀbyꢀoleylamineꢀ(OAm)ꢀandꢀtrioctylphosphineꢀ
conditions,ꢀtheꢀuseꢀofꢀ0.1ꢀmmolꢀPdBr
2
ꢀwithꢀ0.5ꢀorꢀ0.05ꢀmmolꢀ
Ni(ac) ∙4H Oꢀ gaveꢀ Ni@Pdꢀ core‐shellꢀ NPsꢀ withꢀ Ni:Pdꢀ molarꢀ
2
2
ratiosꢀ ofꢀ 5:1ꢀ andꢀ 0.5:1,ꢀ respectively.ꢀ Monometallicꢀ Niꢀ andꢀ Pdꢀ
NPsꢀwereꢀsynthesizedꢀusingꢀtheꢀsameꢀmethod.ꢀ
(TOP)ꢀ toꢀ produceꢀ theꢀ desiredꢀ NPs.ꢀ Subsequently,ꢀ theseꢀ NPsꢀ
wereꢀdepositedꢀonꢀaꢀMIL‐101ꢀmetal‐organicꢀframeworkꢀ(MOF)ꢀ
usingꢀaꢀsimpleꢀimpregnationꢀmethod.ꢀTheꢀnovelꢀMIL‐101ꢀsup‐
portedꢀNi@PdꢀNPsꢀthatꢀresultedꢀwereꢀfoundꢀtoꢀbeꢀhighlyꢀeffi‐
cientꢀinꢀtheꢀreductionꢀofꢀnitroarenesꢀunderꢀmildꢀreactionꢀcondi‐
tions.ꢀCr(III)‐basedꢀMIL‐101,ꢀaꢀmesoporousꢀMOFꢀwithꢀtheꢀmo‐
2.3.ꢀ ꢀ SynthesisꢀofꢀNi@Pd/MIL‐101ꢀandꢀotherꢀcatalystsꢀ
Ni@Pd/MIL‐101ꢀ catalystsꢀ wereꢀ synthesizedꢀ usingꢀ anꢀ
impregnationꢀmethod.ꢀTypically,ꢀ400ꢀmgꢀofꢀactivatedꢀMIL‐101ꢀ
wasꢀdispersedꢀinꢀ10ꢀmLꢀofꢀanhydrousꢀn‐hexaneꢀandꢀstirredꢀforꢀ
1ꢀhꢀatꢀroomꢀtemperature.ꢀTheꢀpreviously‐preparedꢀdispersionꢀ
ofꢀ NPsꢀ inꢀ n‐hexaneꢀ wasꢀ thenꢀ addedꢀ dropwiseꢀ toꢀ theꢀ aboveꢀ
solutionꢀ followedꢀ byꢀ stirringꢀ forꢀ 12ꢀ h.ꢀ Eachꢀ impregnatedꢀ
MIL‐101ꢀ sampleꢀ wasꢀ washedꢀ withꢀ anhydrousꢀ n‐hexaneꢀ untilꢀ
colorlessꢀ filtrateꢀ wasꢀ obtainedꢀ andꢀ thenꢀ slowlyꢀ driedꢀ underꢀ
vacuumꢀatꢀ150ꢀ°Cꢀforꢀ12ꢀhꢀtoꢀobtainꢀNi@Pd/MIL‐101.ꢀSamplesꢀ
ofꢀNi/MIL‐101,ꢀPd/MIL‐101,ꢀandꢀNi@Pd/ACꢀwereꢀsynthesizedꢀ
lecularꢀ formulaꢀ Cr
3
F(H
2
O)
2
O[(O
2
C)C
6
H
4
(CO
2
)]
3
∙nH Oꢀ (nꢀ =ꢀ 25)ꢀ
2
wasꢀchosenꢀbecauseꢀitꢀhasꢀaꢀhighꢀsurfaceꢀarea,ꢀgoodꢀstability,ꢀ
andꢀ numerousꢀ potentiallyꢀ activeꢀ Crꢀ sitesꢀ (upꢀ toꢀ 3.0ꢀ mmol/g)ꢀ
uponꢀremovalꢀofꢀtheꢀterminalꢀwaterꢀmoleculesꢀ[22].ꢀTheꢀLewisꢀ
acidityꢀofꢀMIL‐101ꢀhasꢀbeenꢀdemonstratedꢀtoꢀplayꢀaꢀsignificantꢀ
roleꢀinꢀpromotingꢀtheꢀreactivityꢀofꢀaromaticꢀsubstratesꢀ[2,23].ꢀ
Inꢀaddition,ꢀweꢀhaveꢀpreviouslyꢀshownꢀthatꢀPdꢀNPsꢀcanꢀbeꢀwellꢀ
dispersedꢀonꢀthisꢀMOFꢀandꢀsubsequentlyꢀshowꢀhighꢀactivityꢀandꢀ
stabilityꢀ[24].ꢀ
usingꢀtheꢀsameꢀmethod,ꢀwhileꢀNiPd/MIL‐101ꢀandꢀNi@Pd/En‐
ꢀ
MIL‐101ꢀ wereꢀ synthesizedꢀ followingꢀ proceduresꢀ previouslyꢀ
ꢀ
2.ꢀ ꢀ Experimentalꢀ
reportedꢀinꢀtheꢀliteratureꢀ[25].ꢀTheꢀresultingꢀNiꢀandꢀPdꢀconcen‐
trationsꢀinꢀtheꢀcatalystsꢀwereꢀdeterminedꢀbyꢀAAS.ꢀ
2.1.ꢀ ꢀ Generalꢀ
2.4.ꢀ ꢀ Nitroarenesꢀreductionꢀreactionꢀ
Allꢀchemicalsꢀwereꢀobtainedꢀfromꢀcommercialꢀsourcesꢀandꢀ
wereꢀ usedꢀ withoutꢀ anyꢀ furtherꢀ purification.ꢀ Powderꢀ X‐rayꢀ
diffractionꢀ(XRD)ꢀpatternsꢀofꢀMIL‐101ꢀsamplesꢀwereꢀobtainedꢀ
Theꢀsubstrateꢀ(0.5ꢀmmol),ꢀNi@Pd/MIL‐101ꢀcatalystꢀ(0.023ꢀ
g,ꢀ Pdꢀ 0.2ꢀ mol%),ꢀ andꢀ ethylꢀ acetateꢀ (4ꢀ mL)ꢀ wereꢀ addedꢀ toꢀ aꢀ
Schlenkꢀtube,ꢀandꢀtheꢀmixtureꢀwasꢀvigorouslyꢀstirredꢀwithꢀanꢀ
affixedꢀhydrogenationꢀballoonꢀatꢀroomꢀtemperature.ꢀFollowingꢀ
theꢀreaction,ꢀtheꢀsolidꢀcatalystꢀwasꢀremovedꢀfromꢀtheꢀsolutionꢀ
byꢀfiltrationꢀandꢀwashedꢀwithꢀethylꢀacetate.ꢀTheꢀproductꢀyieldsꢀ
wereꢀ determinedꢀ byꢀ gasꢀ chromatography‐massꢀ spectrometryꢀ
usingꢀaꢀRigakuꢀdiffractometerꢀ(D/MAX‐IIIA,ꢀ3ꢀkW)ꢀwithꢀCuꢀK
α
ꢀ
radiationꢀ (40ꢀ kV,ꢀ 30ꢀ mA,ꢀ λꢀ =ꢀ 0.1543ꢀ nm).ꢀ Brunauer‐Emmett‐
ꢀ
Tellerꢀ(BET)ꢀsurfaceꢀareasꢀandꢀporeꢀvolumesꢀofꢀtheꢀmaterialsꢀ
wereꢀ assessedꢀ withꢀ aꢀ Micromeriticsꢀ ASAPꢀ 2020ꢀ instrumentꢀ
basedꢀonꢀN ꢀadsorptionꢀatꢀ–196ꢀ°Cꢀafterꢀevacuationꢀatꢀ150ꢀ°Cꢀ
2
forꢀ 12ꢀ h.ꢀ Theꢀ Niꢀ andꢀ Pdꢀ contentsꢀ ofꢀ theꢀ samplesꢀ wereꢀ
quantitativelyꢀ determinedꢀ byꢀ atomicꢀ absorptionꢀ spectroscopyꢀ
(GC/MS,ꢀ Shimadzuꢀ GCMS‐QP5050A)ꢀ withꢀ aꢀ 0.25ꢀ mmꢀ ×ꢀ 30ꢀ mꢀ
ꢀ
DB‐WAXꢀcapillaryꢀcolumn.ꢀParametersꢀwereꢀasꢀfollows:ꢀinitialꢀ
ovenꢀ temperature,ꢀ 100ꢀ °C,ꢀ 1ꢀ min;ꢀ ramp,ꢀ 20ꢀ °C/min;ꢀ finalꢀ
temperature,ꢀ280ꢀ°C;ꢀfinalꢀtime,ꢀ5ꢀmin.ꢀ
Duringꢀrecyclabilityꢀtrials,ꢀreactionsꢀwereꢀperformedꢀunderꢀ
theꢀsameꢀconditionsꢀasꢀabove,ꢀexceptꢀusingꢀrecoveredꢀcatalyst.ꢀ
(AAS)ꢀ withꢀ aꢀ HITACHIꢀ Z‐2300ꢀ instrument.ꢀ Fourierꢀ transformꢀ
infraredꢀ (FT‐IR)ꢀ spectraꢀ ofꢀ theꢀ samplesꢀ wereꢀ obtainedꢀ onꢀ aꢀ
Thermoꢀ Scientificꢀ Nicoletꢀ iS10ꢀ spectrometerꢀ withꢀ aꢀ Smartꢀ
OMNIꢀ transmissionꢀ accessory.ꢀ Transmissionꢀ electronꢀ
Jian, Siping
