Superior performance of Co-N/m-C for direct oxidation of alcohols to esters under air

Article abstract of DOI:10.1016/S1872-2067(18)63058-X

A convenient, expeditious, and high-efficiency protocol for the transformation of alcohols into esters using a Co-modified N-doped mesoporous carbon material (Co-N/m-C) as the catalyst is proposed. The catalyst was prepared through direct pyrolysis of a macromolecular precursor. The catalyst prepared using a pyrolysis temperature of 900 °C (labeled Co-N/m-C-900) exhibited the best performance. The strong coordination between the ultra-dispersed cobalt species and the pyridine nitrogen as well as the large area of the mesoporous surface resulted in a high turnover frequency value (107.6 mol methyl benzoate mol^?1 Co h^?1) for the direct aerobic oxidation of benzyl alcohol to methyl benzoate. This value is much higher than those of state-of-the-art transition-metal-based nanocatalysts reported in the literature. Moreover, the catalyst exhibited general applicability to various structurally diverse alcohols, including benzylic, allylic, and heterocyclic alcohols, achieving the target esters in high yields. In addition, a preliminary evaluation revealed that Co-N/m-C-900 can be used six times without significant activity loss. In general, the process was rapid, simple, and cost-effective.

Full text of DOI:10.1016/S1872-2067(18)63058-X

ChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1249–1257
ꢀ
ꢀ ꢀ ꢀ
ꢀ ꢀ ꢀ ꢀ
a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m
ꢀ
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c h n j c
ꢀ
ꢀ
Article
SuperiorꢀperformanceꢀofꢀCo‐N/m‐Cꢀforꢀdirectꢀoxidationꢀofꢀalcoholsꢀ
toꢀestersꢀunderꢀairꢀ
ꢀa,b
ꢀb
ꢀb
ꢀa, ꢀ
ꢀb
ꢀb,#
NingꢀLi ,ꢀSensenꢀShang ,ꢀLianyueꢀWang ,ꢀJingyangꢀNiu *,YingꢀLv ,ꢀShuangꢀGao
ꢀ
aꢀHenanꢀKeyꢀLaboratoryꢀofꢀPolyoxometalateꢀChemistry,ꢀCollegeꢀofꢀChemistryꢀandꢀChemicalꢀEngineering,ꢀHenanꢀUniversity,ꢀKaifengꢀ475004,ꢀHenan,ꢀChinaꢀ
bꢀDalianꢀNationalꢀLaboratoryꢀforꢀCleanꢀEnergy,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences,ꢀDalianꢀ116023,ꢀLiaoning,ꢀChinaꢀ
A R T I C L E ꢀ I N F O ꢀ
A B S T R A C T ꢀ
Articleꢀhistory:ꢀ
Aꢀconvenient,ꢀexpeditious,ꢀandꢀhigh‐efficiencyꢀprotocolꢀforꢀtheꢀtransformationꢀofꢀalcoholsꢀintoꢀestersꢀ
usingꢀaꢀCo‐modifiedꢀN‐dopedꢀmesoporousꢀcarbonꢀmaterialꢀ(Co‐N/m‐C)ꢀasꢀtheꢀcatalystꢀisꢀproposed.ꢀ
Theꢀ catalystꢀ wasꢀ preparedꢀ throughꢀ directꢀ pyrolysisꢀ ofꢀ aꢀ macromolecularꢀprecursor.ꢀTheꢀcatalystꢀ
preparedꢀusingꢀaꢀpyrolysisꢀtemperatureꢀofꢀ900ꢀ°Cꢀ(labeledꢀCo‐N/m‐C‐900)ꢀexhibitedꢀtheꢀbestꢀper‐
formance.ꢀ Theꢀ strongꢀ coordinationꢀ betweenꢀ theꢀ ultra‐dispersedꢀ cobaltꢀ speciesꢀ andꢀ theꢀ pyridineꢀ
nitrogenꢀasꢀwellꢀasꢀtheꢀlargeꢀareaꢀofꢀtheꢀmesoporousꢀsurfaceꢀresultedꢀinꢀaꢀhighꢀturnoverꢀfrequencyꢀ
valueꢀ(107.6ꢀmolꢀmethylꢀbenzoateꢀmol ꢀCoꢀh )ꢀforꢀtheꢀdirectꢀaerobicꢀoxidationꢀofꢀbenzylꢀalcoholꢀtoꢀ
methylꢀ benzoate.ꢀ Thisꢀ valueꢀisꢀmuchꢀ higherꢀthanꢀ thoseꢀofꢀ state‐of‐the‐artꢀ transition‐metal‐basedꢀ
nanocatalystsꢀreportedꢀinꢀtheꢀliterature.ꢀMoreover,ꢀtheꢀcatalystꢀ exhibitedꢀ generalꢀ applicabilityꢀ toꢀ
variousꢀstructurallyꢀdiverseꢀalcohols,ꢀincludingꢀbenzylic,ꢀallylic,ꢀandꢀheterocyclicꢀalcohols,ꢀachievingꢀ
theꢀtargetꢀestersꢀinꢀhighꢀyields.ꢀInꢀaddition,ꢀaꢀpreliminaryꢀevaluationꢀrevealedꢀthatꢀCo‐N/m‐C‐900ꢀ
canꢀbeꢀusedꢀsixꢀtimesꢀwithoutꢀsignificantꢀactivityꢀloss.ꢀInꢀgeneral,ꢀtheꢀprocessꢀwasꢀrapid,ꢀsimple,ꢀandꢀ
cost‐effective.ꢀ
Receivedꢀ9ꢀJanuaryꢀ2018ꢀ
Acceptedꢀ24ꢀFebruaryꢀ2018ꢀ
Publishedꢀ5ꢀJulyꢀ2018ꢀ
Keywords:ꢀ
Cobaltꢀ
N‐dopedꢀ
Mesoporousꢀcarbonꢀ
Estersꢀ
Catalysis
–1
–1
©ꢀ2018,ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀSciences.
PublishedꢀbyꢀElsevierꢀB.V.ꢀAllꢀrightsꢀreserved.
1
.ꢀ ꢀ Introductionꢀ
gle‐stepꢀ directꢀ oxidativeꢀ esterificationꢀ ofꢀ alcohols,ꢀ inꢀ whichꢀ
readilyꢀ availableꢀ alcoholsꢀ areꢀ usedꢀ asꢀ theꢀ startingꢀ materialsꢀ
insteadꢀ ofꢀ acidsꢀ orꢀ theirꢀ derivatives,ꢀ isꢀ garneringꢀ increasingꢀ
attentionꢀ [15–21].ꢀ Catalystsꢀ forꢀ theꢀ directꢀ transformationꢀ ofꢀ
alcoholsꢀtoꢀestersꢀareꢀmostlyꢀbasedꢀonꢀnobleꢀmetalsꢀ(e.g.,ꢀru‐
thenium,ꢀpalladium,ꢀandꢀgold)ꢀ[22–30].ꢀHowever,ꢀowingꢀtoꢀtheꢀ
limitedꢀ amountsꢀ ofꢀ preciousꢀ metals,ꢀ theꢀ developmentꢀ ofꢀ
non‐noble‐metal‐basedꢀcatalystsꢀforꢀtheꢀdirectꢀoxidativeꢀesteri‐
ficationꢀofꢀalcoholsꢀisꢀcrucialꢀfromꢀtheꢀperspectivesꢀofꢀeconomicꢀ
developmentꢀ andꢀ environmentalꢀ protection.ꢀ Moreover,ꢀ withꢀ
regardꢀtoꢀcatalystꢀseparationꢀandꢀrecycling,ꢀtheꢀemploymentꢀofꢀ
heterogeneousꢀ catalystsꢀ isꢀ moreꢀ sustainableꢀ thanꢀ thatꢀ ofꢀ ho‐
mogeneousꢀcatalysts.ꢀ
Estersꢀareꢀextensivelyꢀutilizedꢀasꢀbuildingꢀblocksꢀinꢀorganicꢀ
synthesis,ꢀandꢀtheyꢀcanꢀalsoꢀbeꢀutilizedꢀinꢀfineꢀchemicals,ꢀagro‐
chemicals,ꢀandꢀpharmaceuticalsꢀ[1].ꢀConventionally,ꢀesterifica‐
tionꢀ strategiesꢀ areꢀ basedꢀ onꢀ theꢀ reactionꢀ ofꢀ carboxylicꢀ acids,ꢀ
anhydrides,ꢀ acylꢀ halides,ꢀ orꢀ ketenesꢀ withꢀ alcohols.ꢀ However,ꢀ
theseꢀcomplicatedꢀreactionꢀprocessesꢀareꢀusuallyꢀaccompaniedꢀ
byꢀreagentꢀwasteꢀandꢀtheꢀproductionꢀofꢀaꢀlargeꢀnumberꢀofꢀun‐
desiredꢀbyproductsꢀ[1–5].ꢀDuringꢀrecentꢀdecades,ꢀanꢀenormousꢀ
amountꢀ ofꢀ effortꢀ hasꢀ beenꢀ focusedꢀ onꢀ theꢀ developmentꢀ ofꢀ
cost‐effectiveꢀandꢀenvironmentallyꢀfriendlyꢀstrategiesꢀforꢀesterꢀ
synthesisꢀ [6–14].ꢀ Ofꢀ allꢀ theꢀ establishedꢀ methodologies,ꢀ sin‐
*
ꢀ
ꢀCorrespondingꢀauthor.ꢀTel/Fax:ꢀ+86‐371‐23886876;ꢀE‐mail:ꢀjyniu@henu.edu.cnꢀ
Correspondingꢀauthor. Tel/Fax:ꢀ+86‐411‐84379248;ꢀE‐mail:ꢀsgao@dicp.ac.cnꢀ
#
ThisꢀworkꢀwasꢀsupportedꢀbyꢀtheꢀNationalꢀNaturalꢀScienceꢀFoundationꢀofꢀChinaꢀ(21773232,ꢀ21403219,ꢀ21773227).ꢀ
DOI:ꢀ10.1016/S1872‐2067(18)63058‐Xꢀ|ꢀhttp://www.sciencedirect.com/science/journal/18722067ꢀ|ꢀChin.ꢀJ.ꢀCatal.,ꢀVol.ꢀ39,ꢀNo.ꢀ7,ꢀJulyꢀ2018ꢀ ꢀ ꢀ

1250ꢀ
NingꢀLiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1249–1257ꢀ
Inꢀ recentꢀ years,ꢀ carbonꢀ materialsꢀ haveꢀ becomeꢀ widelyꢀ ap‐
2.ꢀ ꢀ Experimentalꢀ ꢀ
2.1.ꢀ ꢀ Materialsꢀ ꢀ
pliedꢀ inꢀ manyꢀ fields,ꢀ includingꢀ materialsꢀ chemistry,ꢀ chemicalꢀ
catalysis,ꢀ andꢀ electrochemicalꢀ catalysis,ꢀ owingꢀ toꢀ theirꢀ lowꢀ
costs,ꢀ highꢀ stabilities,ꢀ andꢀ excellentꢀ electrochemicalꢀ perfor‐
manceꢀ[31–37].ꢀFurthermore,ꢀtheꢀintroductionꢀofꢀexoticꢀatomsꢀ
andꢀmetalsꢀcanꢀenhanceꢀtheꢀcatalyticꢀperformanceꢀofꢀpureꢀcar‐
bonꢀmaterials.ꢀThisꢀstrategyꢀisꢀusedꢀtoꢀtuneꢀmaterialꢀcomposi‐
tions,ꢀentireꢀelectronicꢀstructures,ꢀandꢀsurfaceꢀphysicochemicalꢀ
propertiesꢀ toꢀ someꢀ extent,ꢀ constructingꢀ newꢀ activeꢀ sitesꢀ andꢀ
extendingꢀtheꢀapplicationꢀofꢀcarbonaceousꢀmaterialsꢀtoꢀaꢀwiderꢀ
rangeꢀofꢀorganicꢀsynthesesꢀ[38–51].ꢀAccordingly,ꢀcobalt‐basedꢀ
N‐dopedꢀ carbonꢀ materialsꢀ haveꢀ beenꢀ proposedꢀ asꢀ potentialꢀ
cost‐effectiveꢀ andꢀ environmentallyꢀ benignꢀ catalystsꢀ forꢀ theꢀ
directꢀaerobicꢀoxidationꢀofꢀalcoholsꢀtoꢀestersꢀ[31,40,52,53].ꢀ ꢀ
11,11’‐bis(Dipyrido[3,2‐a:2’,3’‐c]phenazinylꢀ (bidppz),ꢀ andꢀ
otherꢀ reagentsꢀ wereꢀ obtainedꢀ fromꢀ commercialꢀ sourcesꢀ andꢀ
usedꢀwithoutꢀfurtherꢀpurification.ꢀ ꢀ
2.2.ꢀ ꢀ PreparationꢀofꢀtheꢀCo‐N/m‐Cꢀcatalystꢀ
ToꢀprepareꢀtheꢀCo‐N/m‐Cꢀcatalyst,ꢀ270ꢀmgꢀbidppzꢀandꢀ122ꢀ
mgꢀCo(OAc)
stirring.ꢀTheꢀmixtureꢀwasꢀthenꢀrefluxedꢀatꢀ160ꢀ°Cꢀforꢀ2ꢀh.ꢀThen,ꢀ
400ꢀmgꢀSiO ꢀ(40ꢀwt%ꢀLudoxꢀHS‐40ꢀcolloidalꢀsilica)ꢀwasꢀaddedꢀ
2 2
·4H Oꢀwereꢀaddedꢀtoꢀ40ꢀmLꢀDMFꢀunderꢀvigorousꢀ
2
Inꢀ2013,ꢀBellerꢀetꢀal.ꢀ[53]ꢀpreparedꢀCo
3
O
4
‐N@CꢀwithꢀCo
3
O
4
ꢀ
intoꢀ theꢀ aboveꢀ mixture,ꢀ whichꢀ wasꢀ vigorouslyꢀ stirredꢀ forꢀ an‐
otherꢀ3ꢀh.ꢀAfterꢀevaporatingꢀtheꢀsolventꢀatꢀ180ꢀ°C,ꢀaꢀcompositeꢀ
ofꢀ Co‐bidppzꢀ andꢀ theꢀ templateꢀ wasꢀ obtainedꢀ andꢀ thenꢀ pyro‐
lyzedꢀatꢀtheꢀdesiredꢀtemperatureꢀforꢀ2ꢀhꢀunderꢀflowingꢀnitro‐
gen.ꢀTheꢀheatingꢀrateꢀwasꢀ5ꢀ°C·min .ꢀGenerally,ꢀCo‐N/m‐Cꢀcat‐
alystꢀwasꢀobtainedꢀuponꢀremovalꢀofꢀtheꢀtemplateꢀbyꢀwashingꢀ
withꢀHFꢀ(10ꢀwt%)ꢀforꢀ24ꢀhꢀunderꢀambientꢀatmosphereꢀatꢀroomꢀ
temperature.ꢀ
nanoparticleꢀsizesꢀinꢀtheꢀrangeꢀ2−80ꢀnmꢀbyꢀpyrolyzingꢀcobaltꢀ
saltsꢀandꢀ1,10‐phenanthrolineꢀadsorbedꢀonꢀVulcanꢀXC72R.ꢀThisꢀ
catalystꢀachievedꢀtheꢀtargetꢀreactionꢀusingꢀ2.5ꢀmol%ꢀCoꢀinꢀ24ꢀh.ꢀ
Inꢀ2015,ꢀJiangꢀetꢀal.ꢀ[31]ꢀandꢀLiꢀetꢀal.ꢀ[52]ꢀalmostꢀsimultaneouslyꢀ
butꢀseparatelyꢀemployedꢀZIF‐8‐derivedꢀCo@C‐Nꢀcontainingꢀ15ꢀ
mol%ꢀ Coꢀ toꢀ completeꢀ theꢀ synthesisꢀ ofꢀ esters,ꢀ withꢀ theꢀ latterꢀ
groupꢀachievingꢀbase‐freeꢀesterificationꢀatꢀroomꢀtemperatureꢀinꢀ
–1
96ꢀh.ꢀVeryꢀrecently,ꢀLiꢀetꢀal.ꢀ[40]ꢀreportedꢀtheꢀpreparationꢀofꢀaꢀ
Mott‐Schottky‐typeꢀ Co@NCꢀ catalystꢀ throughꢀ directꢀ polycon‐
densationꢀ ofꢀ simpleꢀ organicꢀ moleculesꢀ andꢀ inorganicꢀ metalꢀ
2.3.ꢀ ꢀ Characterizationꢀofꢀcatalystsꢀ ꢀ
saltsꢀ inꢀ theꢀ presenceꢀ ofꢀ g‐C
3 4
N ꢀ powder.ꢀ However,ꢀ theꢀ activeꢀ
2
N ꢀadsorption‐desorptionꢀisothermsꢀwereꢀmeasuredꢀusingꢀaꢀ
cobaltꢀspeciesꢀwereꢀpoorlyꢀdispersedꢀowingꢀtoꢀtheꢀpoorꢀther‐
malꢀstabilityꢀofꢀtheꢀsmallꢀorganicꢀcompoundsꢀandꢀtheirꢀrandomꢀ
locationꢀ onꢀ theꢀ carbonꢀ support.ꢀ Thisꢀ unavoidableꢀ agglomera‐
tionꢀofꢀactiveꢀcobaltꢀspeciesꢀduringꢀpyrolysisꢀgreatlyꢀdecreasedꢀ
theꢀatomicꢀcatalyticꢀefficiencyꢀofꢀtheꢀresultantꢀmaterial.ꢀNotably,ꢀ
porousꢀ carbonꢀ materialsꢀ areꢀ betterꢀ catalyticꢀ carriersꢀ thanꢀ
non‐porousꢀ materialsꢀ owingꢀ toꢀ theirꢀ largeꢀ surfaceꢀ areasꢀ andꢀ
diverseꢀporousꢀstructures,ꢀwhichꢀfacilitateꢀaccessꢀtoꢀactiveꢀsitesꢀ
andꢀpromoteꢀtheꢀtransportꢀofꢀactiveꢀoxygenꢀspeciesꢀ[54–56].ꢀ ꢀ
Theꢀdesignꢀandꢀpreparationꢀofꢀefficientꢀcatalystsꢀareꢀessen‐
tialꢀactivitiesꢀinꢀourꢀfield.ꢀAccordingly,ꢀweꢀhaveꢀpreviouslyꢀfab‐
ricatedꢀmesoporousꢀcarbonꢀmaterialsꢀderivedꢀfromꢀmacrocyclicꢀ
compoundsꢀ andꢀ vitaminꢀ B12ꢀ thatꢀ showedꢀ highꢀ activityꢀ inꢀ theꢀ
formationꢀofꢀiminesꢀ[57,58].ꢀWeꢀalsoꢀachievedꢀtheꢀsynthesisꢀofꢀ
nitrilesꢀ usingꢀ cobalt‐modifiedꢀ N‐dopedꢀ mesoporousꢀ carbonꢀ
materialsꢀ[59].ꢀ ꢀ
QuadraSorbꢀSI4ꢀStationꢀatꢀ196ꢀ°C,ꢀandꢀtheꢀsamplesꢀwereꢀde‐
gassedꢀ atꢀ 300ꢀ °Cꢀ forꢀ 6ꢀ hꢀ beforeꢀ measurement.ꢀ Transmissionꢀ
electronꢀ microscopyꢀ (TEM)ꢀ imagesꢀ wereꢀ obtainedꢀ usingꢀ aꢀ
JEM‐2100ꢀ microscope.ꢀ Scanningꢀ electronꢀ microscopyꢀ (SEM)ꢀ
imagesꢀwereꢀobtainedꢀusingꢀaꢀJSM‐7800Fꢀmicroscopeꢀwithꢀanꢀ
accelerationꢀvoltageꢀofꢀ20ꢀkV.ꢀTheꢀCoꢀloadingsꢀofꢀtheꢀcatalystsꢀ
wereꢀmeasuredꢀusingꢀinductivelyꢀcoupledꢀplasmaꢀatomicꢀemis‐
sionꢀ spectroscopyꢀ (ICP‐AES)ꢀ usingꢀ aꢀ Perkin‐Elmerꢀ OPTIMAꢀ
–7
3300DV.ꢀTheꢀdetectionꢀlimitꢀwasꢀ1.0ꢀꢀ10 .ꢀPowderꢀX‐rayꢀdif‐
fractionꢀ (XRD)ꢀ patternsꢀ wereꢀ collectedꢀ onꢀ aꢀ Rigaku/Max‐3Aꢀ
α
X‐rayꢀ diffractometerꢀ usingꢀ Cuꢀ K ꢀ radiationꢀ (λꢀ =ꢀ 1.54178ꢀ Å).ꢀ
X‐rayꢀphotoelectronꢀspectroscopyꢀ(XPS)ꢀanalysisꢀwasꢀconduct‐
edꢀusingꢀaꢀThermoꢀScientificꢀESCALABꢀ250XiꢀwithꢀAlꢀK
α
ꢀradia‐
tionꢀanodeꢀ(hvꢀ=ꢀ1486.6ꢀeV).ꢀ
2.4.ꢀ ꢀ Processꢀforꢀtheꢀsynthesisꢀofꢀmethylꢀbenzoateꢀ ꢀ
Encouragedꢀbyꢀtheseꢀresults,ꢀinꢀtheꢀpresentꢀstudyꢀweꢀhaveꢀ
appliedꢀ cobalt‐modifiedꢀ N‐dopedꢀ mesoporousꢀ carbonꢀ
Aꢀmixtureꢀofꢀ22ꢀmgꢀCo‐N/m‐C‐900ꢀcatalystꢀ(0.44ꢀmol%ꢀCo),ꢀ
1ꢀmLꢀmethanol,ꢀ0.5ꢀmmolꢀofꢀtheꢀcorrespondingꢀalcohol,ꢀandꢀ0.1ꢀ
mmolꢀpotassiumꢀcarbonateꢀwasꢀaddedꢀtoꢀaꢀ10‐mLꢀvial.ꢀTheꢀvialꢀ
wasꢀplacedꢀintoꢀanꢀautoclave,ꢀthenꢀtheꢀautoclaveꢀwasꢀfilledꢀwithꢀ
airꢀtoꢀ1ꢀbar.ꢀTheꢀmixtureꢀwasꢀstirredꢀatꢀ60ꢀ°Cꢀforꢀ2ꢀh.ꢀAfterꢀtheꢀ
reaction,ꢀ theꢀ autoclaveꢀ wasꢀ removedꢀ andꢀ cooledꢀ toꢀ ambientꢀ
temperature.ꢀTheꢀairꢀinsideꢀtheꢀautoclaveꢀwasꢀdischargedꢀandꢀ
theꢀ vialꢀ wasꢀ removedꢀ fromꢀ theꢀ autoclave,ꢀ thenꢀ biphenylꢀ wasꢀ
addedꢀtoꢀtheꢀvialꢀasꢀaꢀstandard.ꢀTheꢀreactionꢀsolutionꢀwasꢀdi‐
lutedꢀwithꢀmethanol,ꢀandꢀthenꢀcentrifugedꢀandꢀanalyzedꢀbyꢀgasꢀ
chromatographyꢀ (GC)ꢀ andꢀ gasꢀ chromatography‐massꢀ spec‐
trometryꢀ(GC‐MS)ꢀquantitativelyꢀandꢀqualitatively.ꢀ
(Co‐N/m‐C)ꢀ toꢀ theꢀ aerobicꢀ oxidativeꢀ esterificationꢀ ofꢀ alcoholsꢀ
withꢀairꢀasꢀaꢀbenignꢀoxidant,ꢀachievingꢀexcellentꢀcatalyticꢀactiv‐
ity,ꢀselectivity,ꢀandꢀcatalystꢀrecyclability.ꢀThisꢀoutstandingꢀper‐
formanceꢀ canꢀ beꢀ attributedꢀ toꢀ theꢀ robustꢀ ligandꢀ bridgeꢀ thatꢀ
separatesꢀ theꢀ cobaltꢀ ionsꢀ andꢀ anchorsꢀ themꢀ atꢀ theꢀ molecularꢀ
levelꢀinꢀtheꢀprecursor,ꢀallowingꢀuniformꢀactive‐siteꢀdistributionꢀ
inꢀtheꢀresultantꢀcatalystꢀatꢀtheꢀsub‐nano‐ꢀorꢀatomicꢀscale.ꢀWeꢀ
demonstrateꢀthatꢀtheꢀCo‐N/m‐C‐900ꢀcatalyst,ꢀi.e.,ꢀthatꢀpreparedꢀ
withꢀpyrolysisꢀatꢀ900ꢀ°C,ꢀisꢀtheꢀmostꢀactiveꢀforꢀtheꢀtargetꢀreac‐
tion.ꢀMoreover,ꢀtheꢀresultsꢀofꢀaꢀpreliminaryꢀrecyclingꢀevaluationꢀ
areꢀ reported,ꢀ revealingꢀ thatꢀ Co‐N/m‐C‐900ꢀ canꢀ beꢀ usedꢀ sixꢀ
timesꢀwithoutꢀsignificantꢀlossꢀofꢀactivity,ꢀthusꢀdemonstratingꢀitsꢀ
excellentꢀrecyclability.ꢀ
2.5.ꢀ ꢀ RecyclingꢀofꢀCo‐N/m‐C‐900ꢀ ꢀ

ꢀ
NingꢀLiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1249–1257ꢀ
1251ꢀ
Theꢀ cyclingꢀ testꢀ ofꢀ theꢀ Co‐N/m‐C‐900ꢀ catalystꢀ wasꢀ per‐
formedꢀ basedꢀ onꢀ theꢀ modelꢀ reactionꢀ ofꢀ benzylꢀ alcoholꢀ withꢀ
methanolꢀunderꢀtheꢀfollowingꢀreactionꢀconditions:ꢀAꢀmixtureꢀofꢀ
theꢀreactionꢀscarcelyꢀproceedsꢀwithꢀnoꢀcatalystꢀ(Tableꢀ1,ꢀentryꢀ
1).ꢀSimilarly,ꢀtheꢀCo‐bidppzꢀprecursorꢀshowsꢀlittleꢀconversionꢀ
ofꢀbenzylꢀalcoholꢀ(Tableꢀ1,ꢀentryꢀ2),ꢀconfirmingꢀthat,ꢀunderꢀtheꢀ
conditionsꢀ studied,ꢀ theꢀ Co‐bidppzꢀ precursorꢀ isꢀ inactiveꢀ inꢀ theꢀ
targetꢀreaction.ꢀForꢀcomparison,ꢀweꢀalsoꢀdirectlyꢀpyrolyzedꢀtheꢀ
Co‐bidppzꢀ precursorꢀ withoutꢀ usingꢀ aꢀ template.ꢀ Whenꢀ theꢀ
as‐preparedꢀlow‐surface‐areaꢀCo‐N/Cꢀcatalystꢀ(227ꢀm ·g ,ꢀFig.ꢀ
S1)ꢀisꢀemployed,ꢀtheꢀmethylꢀbenzoateꢀyieldꢀbarelyꢀreachesꢀ0.1%ꢀ
(Tableꢀ 1,ꢀ entryꢀ 3).ꢀ Gratifyingly,ꢀ theꢀ Co‐N/m‐Cꢀ catalystꢀ showsꢀ
excellentꢀ catalyticꢀ performanceꢀ forꢀ thisꢀ transformation,ꢀ yield‐
ingꢀtheꢀproductꢀinꢀ81.6%ꢀyieldꢀ(Tableꢀ1,ꢀentryꢀ4).ꢀConsequently,ꢀ
weꢀdeducedꢀthatꢀpyrolysisꢀatꢀhighꢀtemperatureꢀwasꢀcrucialꢀforꢀ
producingꢀactiveꢀsitesꢀandꢀthatꢀtheꢀexistenceꢀofꢀporosityꢀinꢀtheꢀ
catalystꢀwasꢀimportantꢀforꢀpromotingꢀtheꢀreaction.ꢀ ꢀ
WeꢀalsoꢀpreparedꢀaꢀN/m‐Cꢀcatalystꢀwithoutꢀusingꢀcobaltꢀac‐
etateꢀtetrahydrateꢀbyꢀpyrolysisꢀofꢀbidppzꢀusingꢀaꢀsilicaꢀcolloidꢀ
asꢀaꢀhardꢀtemplateꢀforꢀcomparison.ꢀThisꢀcatalystꢀwasꢀthenꢀap‐
pliedꢀtoꢀtheꢀmodelꢀreaction.ꢀHowever,ꢀnoꢀactivityꢀforꢀesterꢀfor‐
mationꢀ wasꢀ observedꢀ (Tableꢀ 1,ꢀ entryꢀ 5).ꢀ Thus,ꢀ itꢀ mayꢀ beꢀ in‐
ferredꢀ thatꢀ theꢀ cobaltꢀ sitesꢀ conferꢀ theꢀ catalyticꢀ activityꢀ toꢀ theꢀ
material.ꢀ Carbonꢀ materialsꢀ fabricatedꢀ withꢀ otherꢀ non‐nobleꢀ
transitionꢀmetalsꢀprovideꢀlowerꢀconversionsꢀofꢀbenzylꢀalcoholꢀ
thanꢀ thatꢀ achievedꢀ withꢀ cobaltꢀ (Tableꢀ 1,ꢀ entriesꢀ 6−11).ꢀ Thus,ꢀ
theꢀ Co‐N/m‐Cꢀ catalystꢀ isꢀ theꢀ mostꢀ activeꢀ towardsꢀ theꢀ directꢀ
esterificationꢀ ofꢀ benzylꢀ alcoholꢀ withꢀ methanol.ꢀ Consequently,ꢀ
weꢀperformedꢀaꢀseriesꢀofꢀexploratoryꢀexperimentsꢀonꢀtheꢀoxi‐
dativeꢀesterificationꢀofꢀalcoholsꢀemployingꢀthisꢀCo‐basedꢀcata‐
lyst.ꢀ
2
ꢀmmolꢀbenzylꢀalcohol,ꢀ88ꢀmgꢀCo‐N/m‐C‐900,ꢀ4ꢀmLꢀmethanol,ꢀ
andꢀ 0.4ꢀ mmolꢀ potassiumꢀ carbonateꢀ wasꢀ transferredꢀ intoꢀ aꢀ
0‐mLꢀvial.ꢀTheꢀvialꢀwasꢀplacedꢀintoꢀanꢀautoclaveꢀandꢀtheꢀauto‐
claveꢀwasꢀfilledꢀwithꢀO ꢀtoꢀ3ꢀbar.ꢀTheꢀmixtureꢀwasꢀstirredꢀatꢀ60ꢀ
Cꢀforꢀ2ꢀh.ꢀAfterꢀtheꢀreaction,ꢀtheꢀautoclaveꢀwasꢀremovedꢀandꢀ
5
2
–1
2
°
cooledꢀ toꢀ ambientꢀ temperature.ꢀ Theꢀ airꢀ insideꢀ theꢀ autoclaveꢀ
wasꢀdischargedꢀandꢀtheꢀvialꢀwasꢀremovedꢀfromꢀtheꢀautoclave.ꢀ
Theꢀreactionꢀsolutionꢀwasꢀdilutedꢀwithꢀmethanol,ꢀcentrifuged,ꢀ
andꢀthenꢀanalyzedꢀbyꢀGCꢀandꢀGC‐MS.ꢀTheꢀcatalystꢀwasꢀcalcinedꢀ
–1
atꢀ400ꢀ°Cꢀforꢀ2ꢀhꢀusingꢀaꢀheatingꢀrateꢀofꢀ5ꢀ°C·min ꢀinꢀaꢀnitrogenꢀ
atmosphereꢀandꢀthenꢀappliedꢀtoꢀtheꢀnextꢀrun.ꢀTheꢀconversionꢀ
andꢀyieldꢀofꢀeachꢀrunꢀwereꢀconfirmedꢀbyꢀGC.ꢀ
2
.6.ꢀ ꢀ Processꢀforꢀgram‐scaleꢀreactionsꢀ ꢀ
Aꢀ mixtureꢀ ofꢀ 300ꢀ mgꢀ Co‐N/m‐C‐900ꢀ catalystꢀ (0.25ꢀ mol%ꢀ
Co),ꢀ 10ꢀ mLꢀ methanol,ꢀ 10ꢀ mmolꢀ benzylꢀ alcohol,ꢀ andꢀ 2ꢀ mmolꢀ
potassiumꢀcarbonateꢀwasꢀaddedꢀtoꢀaꢀ50‐mLꢀvial.ꢀTheꢀvialꢀwasꢀ
putꢀintoꢀanꢀautoclaveꢀandꢀtheꢀautoclaveꢀwasꢀfilledꢀwithꢀO ꢀtoꢀ5ꢀ
2
bar.ꢀTheꢀmixtureꢀwasꢀstirredꢀatꢀ80ꢀ°Cꢀforꢀ24ꢀh.ꢀAfterꢀtheꢀreac‐
tion,ꢀ theꢀ autoclaveꢀ wasꢀ removedꢀ andꢀ cooledꢀ toꢀ ambientꢀ tem‐
perature.ꢀTheꢀO ꢀinsideꢀtheꢀautoclaveꢀwasꢀdischargedꢀandꢀtheꢀ
2
vialꢀwasꢀremovedꢀfromꢀtheꢀautoclave.ꢀTheꢀreactionꢀsolutionꢀwasꢀ
dilutedꢀ withꢀ methanol,ꢀ centrifuged,ꢀ andꢀ analyzedꢀ byꢀ GCꢀ andꢀ
GC‐MS.ꢀ
Toꢀ determineꢀ theꢀ optimumꢀ catalystꢀ preparationꢀ tempera‐
ture,ꢀ catalystsꢀ preparedꢀ atꢀ differentꢀ pyrolysisꢀ temperaturesꢀ
wereꢀutilizedꢀinꢀtheꢀmodelꢀreaction.ꢀAsꢀseenꢀfromꢀTableꢀ2,ꢀwhenꢀ
theꢀcatalystꢀpyrolyzedꢀatꢀ900ꢀ°Cꢀisꢀappliedꢀinꢀtheꢀoxidativeꢀes‐
terificationꢀofꢀbenzylꢀalcohol,ꢀitꢀaffordsꢀtheꢀtargetꢀproductꢀme‐
thylꢀbenzoateꢀinꢀ94.7%ꢀyieldꢀinꢀonlyꢀ2ꢀh,ꢀthusꢀdemonstratingꢀ
theꢀbestꢀactivityꢀandꢀefficiencyꢀamongꢀtheꢀas‐preparedꢀcatalystsꢀ
(Tableꢀ 2,ꢀ entriesꢀ 1−4).ꢀ Asꢀ theꢀ bestꢀ catalystꢀ inꢀ thisꢀ work,ꢀ
Co‐N/m‐C‐900ꢀprovidesꢀtheꢀhighꢀturnoverꢀfrequencyꢀ(TOF)ꢀofꢀ
3
.ꢀ ꢀ Resultsꢀandꢀdiscussionꢀ
Weꢀcarriedꢀoutꢀaꢀpreliminaryꢀscreeningꢀofꢀdifferentꢀcatalyticꢀ
materialsꢀinꢀorderꢀtoꢀidentifyꢀtheꢀoneꢀwithꢀtheꢀhighestꢀcatalyticꢀ
performanceꢀusingꢀtheꢀreactionꢀofꢀbenzylꢀalcoholꢀwithꢀmetha‐
nolꢀasꢀtheꢀmodelꢀsystem.ꢀGenerally,ꢀreactionsꢀwereꢀconductedꢀ
atꢀ60ꢀ°Cꢀusingꢀ1ꢀbarꢀO .ꢀTheꢀresultsꢀareꢀshownꢀinꢀTableꢀ1.ꢀTheꢀ
blankꢀ experimentꢀ (notꢀ usingꢀ anyꢀ catalyst)ꢀ demonstratesꢀ thatꢀ
2
–1
–1
107.6ꢀmolꢀmethylꢀbenzoateꢀmol ꢀCoꢀh ꢀforꢀtheꢀdirectꢀoxidationꢀ
Tableꢀ1ꢀ
ofꢀ benzylꢀ alcohol.ꢀ Thisꢀ TOFꢀ valueꢀ isꢀ anꢀ orderꢀ ofꢀ magnitudeꢀ
higherꢀthanꢀtheꢀvaluesꢀreportedꢀ forꢀcurrentꢀ Co‐basedꢀhetero‐
geneousꢀcatalysts,ꢀalthoughꢀtheꢀTOFꢀvalueꢀthatꢀobtainedꢀunderꢀ
base‐freeꢀ conditionsꢀ overꢀ Co‐N/m‐C‐900ꢀ isꢀ notꢀ theꢀ highestꢀ
Resultsꢀobtainedꢀusingꢀdifferentꢀcatalystsꢀforꢀtheꢀesterificationꢀofꢀbenzylꢀ
alcoholꢀandꢀmethanol.ꢀ
aꢀ
Tableꢀ2ꢀ
aꢀ
Co‐N/m‐Cꢀcatalyzedꢀesterificationꢀofꢀbenzylꢀalcoholꢀandꢀmethanol.ꢀ
b
b
Entryꢀ
Catalystꢀ
–ꢀ
Co‐bidppzꢀ
Co‐N/Cꢀ
Co‐N/m‐Cꢀ
N/m‐Cꢀ
Fe‐N/m‐Cꢀ
Cu‐N/m‐Cꢀ
V‐N/m‐Cꢀ
Cr‐N/m‐Cꢀ
Ni‐N/m‐Cꢀ
Mn‐N/m‐Cꢀ
Conversionꢀ ꢀ(%)ꢀ Yieldꢀ ꢀ(%)ꢀ
1
ꢀ
traceꢀ
12.7ꢀ
18.6ꢀ
91.6ꢀ
12.0ꢀ
44.1ꢀ
34.5ꢀ
23.8ꢀ
25.6ꢀ
26.8ꢀ
33.6ꢀ
0.0ꢀ
traceꢀ
0.1ꢀ
81.6ꢀ
traceꢀ
1.6ꢀ
0.5ꢀ
0.2ꢀ
0.7ꢀ
1.9ꢀ
2
ꢀ
3
ꢀ
4
ꢀ
ꢀ
c
b
b
5ꢀ ꢀ
Entryꢀ
1ꢀ
Catalystꢀ
Conversionꢀ ꢀ(%) Yieldꢀ ꢀ(%)ꢀ
6
ꢀ
Co‐N/m‐C‐600ꢀ
Co‐N/m‐C‐700ꢀ
Co‐N/m‐C‐800ꢀ
Co‐N/m‐C‐900ꢀ
Co‐N/m‐C‐900ꢀ
Co‐N/m‐C‐900ꢀ
61.0ꢀ
83.1ꢀ
84.3ꢀ
97.5ꢀ
87.1ꢀ
96.3ꢀ
32.5ꢀ
78.7ꢀ
71.5ꢀ
94.7ꢀ
72.8ꢀ
92.9ꢀ
7
ꢀ
2ꢀ
c
8
ꢀ
3ꢀ ꢀ
c
9
1
1
ꢀ
0ꢀ
1ꢀ
4ꢀ ꢀ
d
5ꢀ ꢀ
e
0.6ꢀ
6ꢀ ꢀ
aꢀ Reactionꢀ conditions:ꢀ catalystꢀ (0.44ꢀ mol%ꢀ metal),ꢀ 0.5ꢀ mmolꢀ benzylꢀ
aꢀ Reactionꢀ conditions:ꢀ 0.5ꢀ mmolꢀ 1a,ꢀ 1ꢀ mLꢀ CH
3
OH,ꢀ Co‐N/m‐Cꢀ catalystꢀ
b
b
alcohol,ꢀ1ꢀmLꢀCH
3
OH,ꢀ0.2ꢀequivꢀK
2
3
CO ,ꢀ1ꢀbarꢀO
2
,ꢀ6ꢀh,ꢀ60ꢀ°C.ꢀ ꢀGCꢀandꢀ
(0.44ꢀmol%ꢀCo),ꢀ0.2ꢀequiv.ꢀK
usingꢀbiphenylꢀasꢀstandard.ꢀ ꢀ2ꢀh.ꢀ ꢀ0.5ꢀh.ꢀ ꢀ1ꢀbarꢀair,ꢀ2ꢀh.ꢀ
2
CO
3
,ꢀ1ꢀbarꢀO
2
,ꢀ3ꢀh,ꢀ60ꢀ°C.ꢀ ꢀGCꢀandꢀGC‐MS,ꢀ
c
c
d
e
GC‐MS,ꢀusingꢀbiphenylꢀasꢀstandard.ꢀ ꢀ50ꢀmg,ꢀ24ꢀh,ꢀ60ꢀ°C.ꢀ

1252ꢀ
NingꢀLiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1249–1257ꢀ
(Tableꢀ S1,ꢀ S2).ꢀ Evenꢀ withinꢀ onlyꢀ 0.5ꢀ h,ꢀ theꢀ methylꢀ benzoateꢀ
1600
yieldꢀreachesꢀ72.8%ꢀ(Tableꢀ2,ꢀentryꢀ5),ꢀwhichꢀconfirmsꢀtheꢀout‐
standingꢀ catalyticꢀ efficiencyꢀ ofꢀ ourꢀ selectedꢀ catalyst.ꢀ Notably,ꢀ
thisꢀ catalystꢀ systemꢀ isꢀ stableꢀ andꢀ canꢀ beꢀ reusedꢀ atꢀ leastꢀ fiveꢀ
times.ꢀAꢀyieldꢀofꢀ92.9%ꢀisꢀachievedꢀwhenꢀairꢀisꢀusedꢀasꢀtheꢀoxi‐
dantꢀ(Tableꢀ2,ꢀentryꢀ6),ꢀwhichꢀisꢀonlyꢀaꢀlittleꢀlowerꢀthanꢀthatꢀinꢀ
1400
1200
1000
theꢀ presenceꢀ ofꢀ O
presenceꢀofꢀNa CO
ꢀandꢀ2),ꢀwhereasꢀCs
terꢀyieldsꢀ(85.1%−87.4%;ꢀTableꢀS3,ꢀentriesꢀ3–5).ꢀHowever,ꢀtheꢀ
highestꢀyieldꢀisꢀachievedꢀwithꢀK CO3ꢀ(92.9%;ꢀTableꢀS3,ꢀentryꢀ6).ꢀ ꢀ
2
.ꢀ Lowerꢀ productꢀ yieldsꢀ areꢀ obtainedꢀ inꢀ theꢀ
ꢀandꢀNaOHꢀ(58.6%−70.3%,ꢀTableꢀS3,ꢀentriesꢀ
CO ,ꢀKOH,ꢀandꢀK PO ꢀprovideꢀslightlyꢀbet‐
800
600
400
200
0
2
3
1
2
3
3
4
2
Thus,ꢀthisꢀsystematicꢀinvestigationꢀrevealedꢀthatꢀtheꢀoptimalꢀ
reactionꢀ conditionsꢀ wereꢀ 22ꢀ mgꢀ catalystꢀ (0.44ꢀ mol%ꢀ Co),ꢀ 0.2ꢀ
0.0
0.2
0.4
0.6
0.8
1.0
equiv.ꢀofꢀK
2
CO ,ꢀandꢀaꢀreactionꢀtimeꢀofꢀ2ꢀhꢀatꢀ60ꢀ°Cꢀunderꢀairꢀ
3
Relative pressure (P/P0)
atmosphere.ꢀFurthermore,ꢀaꢀveryꢀsmallꢀamountꢀofꢀbenzylꢀben‐
zoateꢀ isꢀ detectedꢀ afterꢀ theꢀ reaction.ꢀ Thus,ꢀ weꢀ speculatedꢀ thatꢀ
theꢀcatalystꢀmightꢀalsoꢀcatalyzeꢀtheꢀself‐esterificationꢀofꢀbenzylꢀ
alcoholꢀ intoꢀ benzylꢀ benzoate.ꢀ Consequently,ꢀ weꢀ performedꢀ aꢀ
self‐esterificationꢀ experimentꢀ withꢀ benzylꢀ alcohol,ꢀ andꢀ foundꢀ
thatꢀbenzylꢀbenzoateꢀisꢀindeedꢀobtainedꢀ(TableꢀS4).ꢀ
Fig.ꢀ2.ꢀN
2
ꢀsorptionꢀisothermsꢀforꢀCo‐N/m‐C‐900.ꢀ
loopꢀisꢀpowerfulꢀevidenceꢀforꢀtheꢀmesoporousꢀpropertiesꢀofꢀtheꢀ
catalystꢀ (Fig.ꢀ 2).ꢀ Onꢀ theꢀ basisꢀ ofꢀ theꢀ Barrett‐Joyner‐Halendaꢀ
BJH)ꢀ model,ꢀ Fig.ꢀ 3ꢀ revealsꢀ aꢀ broadꢀ pore‐sizeꢀ distributionꢀ forꢀ
(
Weꢀ performedꢀ thermogravimetricꢀ analysisꢀ toꢀ exploreꢀ theꢀ
relationshipꢀbetweenꢀtheꢀactivityꢀandꢀstructureꢀofꢀtheꢀcatalysts.ꢀ
AsꢀshownꢀinꢀFig.ꢀ1,ꢀtheꢀbidppzꢀligandꢀexhibitsꢀveryꢀhighꢀthermalꢀ
stability,ꢀwithꢀaꢀtotalꢀweightꢀlossꢀofꢀonlyꢀ24%ꢀatꢀ900ꢀ°C.ꢀHow‐
ever,ꢀ theꢀ Co‐bidppzꢀ coordinationꢀ polymerꢀ exhibitsꢀ significantꢀ
weightꢀlossꢀatꢀ250ꢀ°C.ꢀWhenꢀtheꢀtemperatureꢀisꢀfurtherꢀraisedꢀ
toꢀ700ꢀ°C,ꢀanotherꢀweightꢀlossꢀoccurs,ꢀbringingꢀtheꢀtotalꢀweightꢀ
lossꢀ toꢀ 31%.ꢀ Theꢀ experimentalꢀ resultsꢀ givenꢀ inꢀ Tableꢀ 2ꢀ showꢀ
thatꢀtheꢀcatalyticꢀactivityꢀofꢀCo‐N/m‐C‐700ꢀisꢀmuchꢀhigherꢀthanꢀ
thatꢀ ofꢀ Co‐N/m‐C‐600,ꢀ indicatingꢀ thatꢀ mostꢀ activeꢀ sitesꢀ areꢀ
formedꢀaboveꢀ700ꢀ°C.ꢀTheꢀCoꢀcontentsꢀofꢀCo‐N/m‐C‐600,ꢀ700,ꢀ
Co‐N/m‐C‐900ꢀrangingꢀfromꢀ1.0ꢀtoꢀ82.8ꢀnm,ꢀinꢀwhichꢀtheꢀpri‐
maryꢀporeꢀsizeꢀisꢀ7.3ꢀnm.ꢀTheꢀBrunauer‐Emmett‐Tellerꢀ(BET)ꢀ
surfaceꢀ areasꢀ ofꢀ Co‐N/m‐C‐700,ꢀ Co‐N/m‐C‐800,ꢀ andꢀ
2
–1
Co‐N/m‐C‐900ꢀareꢀ506,ꢀ680,ꢀandꢀ641ꢀm ·g .ꢀThus,ꢀtheꢀexperi‐
mentalꢀ resultsꢀ showꢀ thatꢀ thereꢀ isꢀ noꢀ positiveꢀ correlationꢀ be‐
tweenꢀcatalystꢀactivityꢀandꢀspecificꢀsurfaceꢀarea.ꢀTheꢀmesopo‐
rousꢀ surfaceꢀ areasꢀ ofꢀ Co‐N/m‐C‐700,ꢀ Co‐N/m‐C‐800,ꢀ
2
–1
Co‐N/m‐C‐900ꢀareꢀ424,ꢀ523ꢀandꢀ502ꢀm ·g .ꢀ ꢀ
ToꢀexploreꢀtheꢀtexturalꢀpropertiesꢀofꢀtheꢀsuperiorꢀCo‐basedꢀ
catalyst,ꢀtheꢀSEMꢀanalysisꢀofꢀCo‐N/m‐C‐900ꢀwasꢀconductedꢀandꢀ
theꢀ resultsꢀ areꢀ displayedꢀ inꢀ Fig.ꢀ 4(a).ꢀ Aꢀ sponge‐likeꢀ surfaceꢀ
morphologyꢀpossessingꢀaꢀlargeꢀnumberꢀofꢀdenseꢀporesꢀisꢀob‐
served,ꢀclearlyꢀindicatingꢀtheꢀintroductionꢀofꢀsphericalꢀholesꢀinꢀ
theꢀ preparedꢀ materials.ꢀ Weꢀ examinedꢀ Co‐N/m‐C‐900ꢀ usingꢀ
TEMꢀ toꢀ obtainꢀ furtherꢀ detailedꢀ structuralꢀ information.ꢀ Manyꢀ
poresꢀareꢀobservedꢀwithꢀporeꢀsizesꢀrangingꢀfromꢀaꢀfewꢀtoꢀsev‐
eralꢀtensꢀofꢀnanometers,ꢀwhichꢀagreesꢀwithꢀtheꢀaboveꢀSEMꢀre‐
sultsꢀ andꢀ confirmsꢀ theꢀ specialꢀ porousꢀ structureꢀ ofꢀ
Co‐N/m‐C‐900.ꢀNoꢀtypicalꢀdiffractionꢀpatternsꢀareꢀdisplayedꢀinꢀ
800,ꢀandꢀ900ꢀareꢀ0.18,ꢀ0.27,ꢀ0.44,ꢀandꢀ0.59ꢀwt%,ꢀrespectively,ꢀ
revealingꢀthatꢀmoreꢀactiveꢀcobaltꢀspeciesꢀareꢀgeneratedꢀinꢀtheꢀ
high‐temperatureꢀrangeꢀ(700−900ꢀ°C).ꢀAsꢀdiscussedꢀabove,ꢀtheꢀ
highestꢀ activityꢀ inꢀ theꢀ targetꢀ reactionꢀ isꢀ achievedꢀ overꢀ
Co‐N/m‐C‐900ꢀsamples.ꢀ ꢀ
N
2
ꢀ adsorptionꢀ analysisꢀ wasꢀ carriedꢀ outꢀ toꢀ investigateꢀ theꢀ
highꢀcatalyticꢀactivityꢀofꢀCo‐N/m‐C‐900.ꢀTheꢀH4‐typeꢀhysteresisꢀ
0.25
0.20
0.15
0.10
0.05
1
00
bidppz
80
60
40
20
Co-bidppz
0
200
400
600
800
1000
o
Temperature ( C)
0.00
0
20
40
60
80
Fig.ꢀ1.ꢀThermogravimetricꢀcurveꢀofꢀdifferentꢀprecursorsꢀrecordedꢀun‐
Pore diameter (nm)
–1
derꢀN ꢀatmosphereꢀatꢀaꢀheatingꢀrateꢀofꢀ10ꢀ°C∙min .ꢀ
2
Fig.ꢀ3.ꢀBJHꢀpore‐sizeꢀdistributionꢀplotꢀforꢀCo‐N/m‐C‐900.ꢀ

ꢀ
NingꢀLiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1249–1257ꢀ
1253ꢀ
(a)
(b)
(a)
Co-O
(
779.8 eV)
Co-N
781.6 eV)
(
Spinels
Vacc=1.00kv Detector=UED PC=4 Mode=GB Vgun=3.00kv
(c)
C‐Kα
O‐Kα
N‐Kα
7
92
790
788
786
784
782
780
778
776
774
Co‐Kα
Binding energy (eV)
Fig.ꢀ6.ꢀCoꢀ2p3/2ꢀXPSꢀspectraꢀofꢀCo‐N/m‐C‐900.
Fig.ꢀ 4.ꢀ Microstructuralꢀ observationꢀ ofꢀ theꢀ Co‐N/m‐C‐900ꢀ catalystꢀ (a)
SEMꢀimage;ꢀ(b)ꢀTEMꢀimage;ꢀ(c)ꢀLarge‐areaꢀSEMꢀimageꢀandꢀtheꢀcorre‐
spondingꢀelementalꢀmaps.ꢀ
lystsꢀ(Fig.ꢀ5,ꢀFig.ꢀ6,ꢀFig.ꢀS5).ꢀTheꢀNꢀ1sꢀspectrumꢀofꢀtheꢀcatalystꢀ
couldꢀonlyꢀbeꢀdeconvolutedꢀintoꢀtwoꢀcomponents,ꢀi.e.,ꢀpyridinicꢀ
nitrogenꢀ(398.6ꢀeV)ꢀcoordinatingꢀtoꢀaꢀcobaltꢀionꢀandꢀgraphiticꢀ
theꢀ selected‐areaꢀ electronꢀ diffractionꢀ (SAED)ꢀ image,ꢀ whichꢀ
indicatesꢀ theꢀ polycrystallineꢀ structureꢀ ofꢀ theꢀ Co‐N/m‐C‐900ꢀ
sampleꢀ (Fig.ꢀ S2(c)).ꢀ Moreover,ꢀ theꢀ relevantꢀ energy‐dispersiveꢀ
X‐rayꢀ (EDX)ꢀ spectrumꢀ displayedꢀ inꢀ Fig.ꢀ S2(d)ꢀ confirmsꢀ theꢀ
presenceꢀofꢀcobalt.ꢀHowever,ꢀnanoparticlesꢀthatꢀcontainꢀmetalꢀ
couldꢀ notꢀ beꢀ observed,ꢀ evenꢀ byꢀ HRTEMꢀ (Fig.ꢀ S2(a)ꢀ andꢀ Fig.ꢀ
S2(b)).ꢀ Toꢀ furtherꢀ verifyꢀ this,ꢀ SEMꢀ inꢀ backscatteredꢀ electronꢀ
detectionꢀmodeꢀ(Vaccꢀ=ꢀ10.0ꢀkeV,ꢀprovidingꢀanꢀelectronꢀpenetra‐
tionꢀ depthꢀ atꢀ theꢀ µmꢀ level)ꢀ wasꢀ employedꢀ (Fig.ꢀ S3),ꢀ andꢀ noꢀ
whiteꢀ particlesꢀ areꢀ seen.ꢀ Theꢀ absencesꢀ ofꢀ discernibleꢀ metallicꢀ
2
nitrogenꢀbondedꢀwithꢀthreeꢀsp ꢀcarbonꢀatomsꢀwithinꢀtheꢀgra‐
phiticꢀ planeꢀ (401.0ꢀ eV)ꢀ (Fig.ꢀ 5)ꢀ [60,61].ꢀ Subsequently,ꢀ theꢀ Coꢀ
2p3/2ꢀ XPSꢀ spectrumꢀ ofꢀ theꢀ Co‐N/m‐C‐900ꢀ catalystꢀ wasꢀ fittedꢀ
intoꢀtwoꢀdistinctꢀpeaksꢀcenteredꢀatꢀ781.6ꢀandꢀ779.8ꢀeVꢀ(Fig.ꢀ6),ꢀ
whichꢀcanꢀbeꢀascribedꢀtoꢀCo−NꢀandꢀCo−O,ꢀrespectivelyꢀ[62].ꢀAsꢀ
shownꢀinꢀFig.ꢀS6ꢀandꢀS7,ꢀtheꢀspecificꢀformsꢀofꢀtheꢀnitrogenꢀdo‐
pantsꢀ andꢀ cobaltꢀ inꢀ Co‐N/m‐C‐700ꢀ andꢀ ‐800ꢀ areꢀ theꢀ sameꢀ asꢀ
thoseꢀinꢀCo‐N/m‐C‐900.ꢀManyꢀresearchersꢀhaveꢀshownꢀthatꢀtheꢀ
specialꢀCoꢀchemicalꢀenvironment,ꢀinꢀwhichꢀpyridinicꢀnitrogenꢀisꢀ
involved,ꢀ playsꢀ anꢀ importantꢀ partꢀ inꢀ furnishingꢀ theꢀ catalystsꢀ
withꢀappropriateꢀactivityꢀinꢀoxidationꢀreactions.ꢀFurthermore,ꢀ
theꢀ N‐dopedꢀ carbonꢀ alsoꢀ helpsꢀ stabilizeꢀ theꢀ activeꢀ Coꢀ speciesꢀ
Coꢀphase,ꢀCo
3
O ,ꢀandꢀCoOꢀspeciesꢀareꢀfurtherꢀconfirmedꢀbyꢀtheꢀ
4
XRDꢀresultsꢀ(Fig.ꢀS4).ꢀMetagenicꢀchainsꢀconsistingꢀofꢀtheꢀligandꢀ
andꢀcobaltꢀcompriseꢀtheꢀCo‐bidppzꢀpolymer,ꢀwhichꢀmayꢀimpedeꢀ
theꢀaggregationꢀofꢀcobaltꢀspeciesꢀwhenꢀtheꢀmaterialꢀisꢀheated.ꢀ
Thus,ꢀ itꢀ isꢀ rationalꢀ toꢀ conjectureꢀ that,ꢀ afterꢀ acidꢀ washing,ꢀ theꢀ
vestigialꢀ activeꢀ cobaltꢀ speciesꢀ mightꢀ existꢀ atꢀ theꢀ sub‐nano‐ꢀ orꢀ
atomicꢀscale,ꢀwhich,ꢀalongꢀwithꢀtheꢀmesoporousꢀmicrostructureꢀ
ofꢀtheꢀcatalyst,ꢀisꢀresponsibleꢀforꢀitsꢀsuperiorꢀcatalyticꢀactivity.ꢀ ꢀ
WeꢀperformedꢀXPSꢀonꢀtheꢀsamplesꢀtoꢀdetermineꢀtheꢀchemi‐
calꢀstatesꢀofꢀtheꢀcobaltꢀandꢀnitrogenꢀinsideꢀtheꢀCo‐N/m‐Cꢀcata‐
[53,63,64].ꢀ
Theꢀproposedꢀmethodologyꢀexhibitsꢀgeneralꢀapplicabilityꢀtoꢀ
theꢀ esterificationꢀ ofꢀ otherꢀ aromaticꢀ alcohols.ꢀ Diverseꢀ benzylicꢀ
alcoholsꢀareꢀoxidizedꢀselectivelyꢀtoꢀtheꢀcorrespondingꢀmethylꢀ
estersꢀinꢀgoodꢀtoꢀexcellentꢀyieldsꢀatꢀ60ꢀ°Cꢀ(Tableꢀ3).ꢀBenzylꢀal‐
coholsꢀ andꢀ alkyl‐substitutedꢀ benzylꢀ alcoholsꢀ areꢀ esterifiedꢀ
convenientlyꢀ inꢀ highꢀ yieldsꢀ ofꢀ upꢀ toꢀ 98.8%ꢀ (Tableꢀ 3,ꢀ entriesꢀ
1−5),ꢀ andꢀ benzylꢀ alcoholsꢀ substitutedꢀ withꢀ otherꢀ elec‐
tron‐donatingꢀ groupsꢀ suchꢀ asꢀ −OCH
3
ꢀ inꢀ theꢀ para‐ꢀ andꢀ me‐
Graphitic N
Pyridinic N/N-Metal
(398.6 eV)
ta‐positionsꢀgiveꢀtheꢀcorrespondingꢀmethylꢀbenzoatesꢀinꢀ96.4%ꢀ
andꢀ91.5%ꢀyieldsꢀ(Tableꢀ3,ꢀentriesꢀ6ꢀandꢀ7).ꢀInꢀaddition,ꢀsub‐
stratesꢀwithꢀhalogenꢀfunctionalꢀgroupsꢀ(−F,ꢀ−Cl,ꢀ−Br)ꢀareꢀesteri‐
fiedꢀtoꢀtheꢀtargetꢀmethylꢀestersꢀinꢀhighꢀyieldsꢀ(Tableꢀ3,ꢀentriesꢀ
(
401.0 eV)
9−11).ꢀ Whenꢀ theꢀ benzylꢀ alcoholꢀ isꢀ substitutedꢀ withꢀ aꢀ strongꢀ
electron‐withdrawingꢀ groupꢀ (−NO ꢀ andꢀ −CF )ꢀ inꢀ theꢀ pa‐
2
3
ra‐position,ꢀslightlyꢀlowerꢀyieldsꢀofꢀtheꢀcorrespondingꢀproductsꢀ
areꢀobtainedꢀ(Tableꢀ3,ꢀentriesꢀ12ꢀandꢀ13).ꢀ ꢀ
Basedꢀonꢀtheꢀaboveꢀresults,ꢀbenzylꢀalcoholsꢀsubstitutedꢀwithꢀ
electron‐donatingꢀandꢀelectron‐withdrawingꢀfunctionalꢀgroupsꢀ
areꢀesterifiedꢀtoꢀtheꢀdesiredꢀmethylꢀestersꢀinꢀsatisfactoryꢀyields.ꢀ
Itꢀisꢀworthyꢀofꢀnoteꢀthatꢀtheꢀmoreꢀsensitiveꢀallylicꢀalcoholꢀisꢀalsoꢀ
moderatelyꢀconvertedꢀtoꢀtheꢀcorrespondingꢀesterꢀinꢀourꢀoxida‐
tiveꢀ esterificationꢀ system,ꢀ providingꢀ theꢀ methylꢀ cinnamateꢀ inꢀ
4
06
404
402
400
398
396
Binding energy (eV)
Fig.ꢀ5.ꢀNꢀ1sꢀXPSꢀspectraꢀofꢀCo‐N/m‐C‐900.ꢀ
80%ꢀyieldꢀ(Tableꢀ3,ꢀentryꢀ14).ꢀ ꢀ

1
254ꢀ
NingꢀLiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1249–1257ꢀ
Tableꢀ4ꢀ
Tableꢀ3ꢀ
Co‐N/m‐C‐900ꢀcatalyzedꢀesterificationꢀofꢀaromaticꢀalcoholsꢀandꢀmeth‐
anol.ꢀ
Co‐N/m‐C‐900ꢀcatalyzedꢀesterificationꢀofꢀbenzylicꢀalcoholsꢀandꢀaliphat‐
aꢀ
aꢀ
icꢀalcohols.ꢀ
Temperatureꢀ Yieldꢀbꢀ
bꢀ
Entry
1ꢀ
R'–OHꢀ
Esterꢀ
Entryꢀ
Alcoholꢀ
Productꢀ
Yieldꢀ (%)
o
(
C)ꢀ
(%)ꢀ
1
2
3
4
ꢀ
ꢀ
ꢀ
92.9ꢀ
ꢀ
80ꢀ
90ꢀ
77.5ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
98.8ꢀ
93.5ꢀ
91.7ꢀ
ꢀ
2
3
4
5
ꢀ
78.3ꢀ
70.0ꢀ
79.1ꢀ
87.4ꢀ
71.8ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
c
ꢀ ꢀ
90ꢀ
c
ꢀ
ꢀ ꢀ
ꢀ
d
ꢀ ꢀ
90ꢀ
ꢀ
8
5.8ꢀ
ꢀ
5
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
d
ꢀ ꢀ
110ꢀ
110ꢀ
ꢀ
6
7
8
ꢀ
ꢀ
ꢀ
96.4ꢀ
91.5ꢀ
89.0ꢀ
ꢀ
d
6
ꢀ ꢀ
ꢀ
a
ꢀReactionꢀconditions:ꢀCo‐N/m‐C‐900ꢀcatalystꢀ(22ꢀmg,ꢀ0.44ꢀmol%ꢀCo),ꢀ
CO ,ꢀ1ꢀbarꢀair,ꢀ1ꢀmLꢀR'–OH,ꢀ6ꢀh.ꢀ ꢀ
.ꢀ ꢀ1ꢀequiv.ꢀK CO ,ꢀ24ꢀh.ꢀ
ꢀ
OH
0.5ꢀmmolꢀbenzylicꢀalcohol,ꢀ0.5ꢀequiv.ꢀK
2
3
b
c
d
ꢀGCꢀandꢀGC‐MS.ꢀ ꢀ0.8ꢀequiv.ꢀK
2
CO
3
2
3
ꢀ
ꢀ
ꢀ
9
1
1
1
ꢀ
90.6ꢀ
87.9ꢀ
94.1ꢀ
82.3ꢀ
variousꢀ benzylicꢀ alcoholsꢀ withꢀ methanol,ꢀ weꢀ exploredꢀ theꢀ se‐
lectiveꢀoxidativeꢀcouplingꢀwithꢀotherꢀaliphaticꢀalcohols.ꢀInꢀfact,ꢀ
veryꢀ littleꢀ researchꢀ hasꢀ beenꢀ carriedꢀ outꢀ forꢀ suchꢀ
cross‐esterifications,ꢀi.e.,ꢀwhenꢀoneꢀalcoholꢀhasꢀtheꢀpossibilityꢀofꢀ
beingꢀoxidizedꢀinꢀtheꢀpresenceꢀofꢀanother.ꢀAsꢀexpected,ꢀbenzylicꢀ
alcoholsꢀ andꢀ ethanolꢀ areꢀ transformedꢀ intoꢀ theꢀ correspondingꢀ
ethylꢀestersꢀinꢀ70.0%−78.3%ꢀyieldꢀ(Tableꢀ4,ꢀentriesꢀ1−3).ꢀForꢀ
propyl,ꢀ butyl,ꢀ andꢀ pentylꢀ alcohols,ꢀ theꢀ desiredꢀ estersꢀ areꢀ ob‐
tainedꢀinꢀ71.8%−87.4%ꢀyieldꢀ(Tableꢀ4,ꢀentriesꢀ4−6).ꢀ
ꢀ
ꢀ
0ꢀ
1ꢀ
2ꢀcꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
Asꢀweꢀallꢀknow,ꢀstabilityꢀandꢀrecyclabilityꢀareꢀcrucialꢀcriteriaꢀ
forꢀtheꢀpracticalꢀapplicationꢀofꢀheterogeneousꢀcatalyticꢀmateri‐
als.ꢀThus,ꢀinꢀorderꢀtoꢀdemonstrateꢀitsꢀreusability,ꢀsixꢀconsecu‐
tiveꢀ oxidativeꢀ esterificationsꢀ ofꢀ benzylꢀ alcoholꢀ withꢀ methanolꢀ
wereꢀ performedꢀ usingꢀ theꢀ Co‐N/m‐C‐900ꢀ catalyst.ꢀ Inꢀ thisꢀ ex‐
periment,ꢀtheꢀ catalystꢀ wasꢀwashedꢀthoroughlyꢀwithꢀmethanolꢀ
afterꢀtheꢀreactionꢀwasꢀover,ꢀandꢀitꢀwasꢀthenꢀcalcinedꢀatꢀ400ꢀ°Cꢀ
d
1
1
1
3ꢀ ꢀ
72.6ꢀ
80.0ꢀ
98.8ꢀ
ꢀ
ꢀ
4ꢀeꢀ
5ꢀ
ꢀ
ꢀ
ꢀ
ꢀ
underꢀN
ꢀforꢀ2ꢀhꢀbeforeꢀbeingꢀemployedꢀinꢀtheꢀnextꢀrun.ꢀTheꢀ
2
1
6ꢀcꢀ
88.3ꢀ
resultsꢀ revealedꢀ thatꢀ theꢀ Co‐N/m‐C‐900ꢀ catalystꢀ canꢀ beꢀ recy‐
cledꢀsuccessfullyꢀfiveꢀtimesꢀwithꢀnoꢀapparentꢀlossꢀofꢀcatalyticꢀ
activityꢀ(Fig.ꢀ7).ꢀ
ꢀ
ꢀ
aꢀReactionꢀconditions:ꢀCo‐N/m‐C‐900ꢀcatalystꢀ(22ꢀmg,ꢀ0.44ꢀmol%ꢀCo),ꢀ
.5ꢀmmolꢀ1,ꢀ0.2ꢀequiv.ꢀK
andꢀGC‐MS.ꢀ ꢀ6ꢀh,ꢀ80ꢀ°C,ꢀ ꢀ16ꢀh,ꢀ80ꢀ°C,ꢀ ꢀ12ꢀh,ꢀ60ꢀ°C.ꢀ
b
0
2
CO
3
,ꢀ1ꢀmLꢀmethanol,ꢀ1ꢀbarꢀair,ꢀ2ꢀh,ꢀ60ꢀ°C.ꢀ ꢀGCꢀ
Theꢀ catalyticꢀ experimentsꢀ aboveꢀ wereꢀ conductedꢀ atꢀ theꢀ
c
d
e
0.5−2ꢀmmolꢀscale.ꢀTherefore,ꢀweꢀwereꢀinterestedꢀinꢀexploringꢀ
Next,ꢀweꢀstudiedꢀtheꢀoxidativeꢀesterificationꢀofꢀheterocyclicꢀ
alcohols.ꢀ Piperonylꢀ alcoholꢀ isꢀ transformedꢀ intoꢀ methylꢀ
theꢀ syntheticꢀ utilityꢀofꢀthisꢀmethodologyꢀinꢀtermsꢀofꢀ scale‐up.ꢀ
Therefore,ꢀweꢀperformedꢀreactionsꢀforꢀsomeꢀsubstratesꢀatꢀtheꢀ
10ꢀmmolꢀscale.ꢀAsꢀshownꢀinꢀSchemeꢀ1,ꢀtheꢀcorrespondingꢀme‐
thylꢀestersꢀareꢀobtainedꢀinꢀyieldsꢀofꢀupꢀtoꢀ96.1%.ꢀThus,ꢀourꢀcat‐
alystꢀsystemꢀisꢀapplicableꢀtoꢀtheꢀlab‐scaleꢀdirectꢀesterificationꢀofꢀ
alcoholsꢀinꢀrelativelyꢀshortꢀreactionꢀtimesꢀusingꢀairꢀasꢀaꢀbenignꢀ
oxidant.ꢀ
1,3‐benzodioxole‐5‐carboxylateꢀinꢀtheꢀexcellentꢀyieldꢀofꢀ98.8%ꢀ
(Tableꢀ3,ꢀentryꢀ15),ꢀandꢀtheꢀesterificationꢀofꢀ3‐thienylmethanolꢀ
givesꢀ theꢀ productꢀ inꢀ theꢀ satisfactoryꢀ yieldꢀ ofꢀ 88.3%ꢀ (Tableꢀ 3,ꢀ
entryꢀ16).ꢀ ꢀ
Afterꢀobtainingꢀ satisfactoryꢀresultsꢀforꢀtheꢀesterificationꢀofꢀ

ꢀ
NingꢀLiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1249–1257ꢀ
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4.ꢀ ꢀ Conclusionsꢀ
[
[
[
Weꢀhaveꢀdevelopedꢀanꢀefficientꢀandꢀinexpensiveꢀstrategyꢀforꢀ
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NingꢀLi,ꢀSensenꢀShang,ꢀLianyueꢀWang,ꢀJingyangꢀNiu*,ꢀYingꢀLv,ꢀShuangꢀGao*ꢀ
HenanꢀUniversity;ꢀDalianꢀInstituteꢀofꢀChemicalꢀPhysics,ꢀChineseꢀAcademyꢀofꢀ
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cobalt‐modifiedꢀ N‐dopedꢀ mesoporousꢀ carbonꢀ materialꢀ (Co‐N/m‐C)ꢀ asꢀ theꢀ
catalystꢀunderꢀairꢀatmosphere.ꢀ

1256ꢀ
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Co-N/m-C 高效催化空气下醇直接氧化成酯
a,b
b
b
a,*
b
b,#
李 宁 , 尚森森 , 王连月 , 牛景杨 , 吕 迎 , 高 爽
a
河南大学化学化工学院河南省多酸化学重点实验室, 河南开封 475000
b
中国科学院大连化学物理研究所, 辽宁大连 116023
摘要: 酯类在有机合成中作为基础材料广泛地应用于精细化学品, 农用化学品, 药物等的生产中. 传统生产酯的方法需要
用到羧酸, 酸酐, 酰卤或酮类, 并经过多步反应完成. 往往会造成原材料的浪费, 并伴随副产物的产生. 因此用醇代替酸或
其衍生物与另一种醇反应直接氧化酯化合成相应的酯具有很大的经济意义. 目前已有基于贵金属(如钌, 钯和金)的将醇类
直接氧化为酯类的催化剂的研究, 但是贵金属的价格及其有限的资源限制了其在实际生产中的应用. 从经济发展和环境
保护的角度出发, 开发基于非贵金属的用于醇氧化酯化的催化剂有重要意义.
近年来, 碳材料由于成本低、 稳定性高、 电化学性能优异的特点而广泛应用于材料、 化学催化和电化学催化等领
域. 此外, 杂原子和金属的引入可以在一定程度上调节材料的组成, 电子结构和表面物理化学性质而进一步构建新的活性
位点, 增强碳材料的催化性能. 另外, 由于多孔碳材料具有较大的比表面积和多样的孔结构, 作为催化剂载体比普通碳材
料更优越, 使得底物更容易接触活性部位, 同时提高氧的传输能力. 然而, 活性钴物种因在热解过程中容易发生团聚而使
原子催化效率降低. 因此设计和制备高分散且高效的催化剂对于实现醇氧化为酯有重要意义.

ꢀ
NingꢀLiꢀetꢀal.ꢀ/ꢀChineseꢀJournalꢀofꢀCatalysisꢀ39ꢀ(2018)ꢀ1249–1257ꢀ
1257ꢀ
钴基氮掺杂碳材料是一种有潜力的能将醇直接氧化到酯的经济, 高效, 环保的催化剂. 本文提出了一种方便, 快捷, 高
效的醇直接氧化成酯的方法, 即利用直接热解大分子前驱体制备钴改性N掺杂介孔碳材料(Co-N/m-C), 用于醇直接氧化成
o
酯反应中, 其中以900 C下焙烧所制的催化剂活性最高. 该催化剂对于苯甲醇直接有氧氧化成苯甲酸甲酯反应的TOF值高
1
−
达107.6 h , 远高于目前所报道的过渡金属基纳米催化剂的, 这得益于超分散钴物种与材料中吡啶氮之间的强配位作用及
大的介孔比表面积. 对于不同结构的醇, 包括苄基醇, 烯丙基醇和杂环醇, 也能高收率地得到相应酯, 说明该催化剂具有普
适性. 另外, Co-N/m-C-900催化剂经循环使用六次后没有显著的活性损失, 表明了该催化剂具有一定的稳定性.
关键词: 钴; 氮掺杂; 介孔碳材料; 酯; 催化
收稿日期: 2018-01-09. 接受日期: 2018-02-24. 出版日期: 2018-07-05.
*
通讯联系人. 电话/传真: (0371)23886876; 电子信箱: jyniu@henu.edu.cn
#
通讯联系人. 电话/传真: (0411)84379248; 电子信箱: sgao@dicp.ac.cn
基金来源: 国家自然科学基金 (21773232, 21403219, 21773227).
本文的电子版全文由Elsevier出版社在ScienceDirect上出版(http://www.sciencedirect.com/science/journal/18722067).