Solid acid catalysts are widely used in the production of various high-value added and industrially important chemicals.Although the use of organosilicon compounds to modify the vacancy site has been extensively studied,the covalent tethering-SO3H functionalized organosilicon modified polyoxometalates(POMs)has been rarely reported.In this work,two catalysts(TBA4[SiW11O39(O(SiC3H6SO3H)2)](compound 2)and TBA4[SiW11O39(O(SiC8H8SO3H)2)](compound 3))were synthesized successfully through covalently grafting different sulfonic acid(-SO3H)groups onto[SiW11O39]8-cluster,respectively.Com-pound 2 was achieved by surface grafting and in situ oxidation(3-mercaptopropyl)-trimethoxysilane,while compound 3 was achieved by surface grafting of 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane.Strong Br?nsted acid strength of compounds 2 and 3 can be demonstrated by different methods including potentiometric titration,pyridine adsorption studies,and the P trimethylphosphine oxides(TMPO)nuclear magnetic resonance(NMR).The systematic investigation of the relationship among POM structures,acid strength,and electron density was carried out based on density functional theory(DFT)calculation and experimental results,which revealed that covalent modification of compounds 2 and 3 decreased the electron density of the O-H bond,and promoted the release of H+.When applied in hydroxyalkylation/alkylation(HAA)reaction of 2-methylfuran(2-MF)with cyclohexanone,compound 2 exhibited better catalytic performance with conversion of～93％,monocyclic fuel precursors(1a)yield of 79.9％and selectivity of 85.7％than compound 3,which can be attributed to strong Br?nsted acid and the intramolecular hydrogen-bonding interactions between the neighboring-SO3H moieties in compound 2.Finally,compound 2 also showed excellent catalytic activity in the HAA reaction of 2-MF with several different aldehydes and ketones(e.g.,furfuraldehyde,5-methylfurfuraldehyde,acetone,butyraldehyde and 4-methoxybenzaldehyde).This result opens a new pathway for design and fabrication of novel solid acid catalysts.

Lifei Lian;Yubing Liu;Xianfeng Yi;Hanbin Hu;Xiang Chen;Hongqiang Li;Wei Chen;Anming Zheng;Yu-Fei Song

State Key Laboratory of Chemical Resource Engineering,Beijing University of Chemical Technology,Beijing 100029,China;Wuhan Center for Magnetic Resonance,Key Laboratory of Magnetic Resonance in Biological Systems,State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics,Wuhan Institute of Physics and Mathematics,Chinese Academy of Sciences,Wuhan 430071,China

中国科学:化学（英文版）

[1]Lifei Lian;Yubing Liu;Xianfeng Yi;Hanbin Hu;Xiang Chen;Hongqiang Li;Wei Chen;Anming Zheng;Yu-Fei Song-.Covalently tethering disulfonic acid moieties onto polyoxometalate boosts acid strength and catalytic performance for hydroxyalkylation/alkylation reaction)[J].中国科学:化学（英文版）,2022(04):699-709

Covalently,disulfonic,hydroxyalkylation,organosilicon,TBA4,SiW11O39,SiC3H6SO3H,SiC8H8SO3H,mercaptopropyl,trimethoxysilane,chlorosulfonylphenyl,ethyltrimethoxysilane,trimethylphosphine,TMPO,methylfuran,furfuraldehyde,methylfurfuraldehyde,butyraldehyde

tethering,acid,moieties,onto,boosts,strength,catalytic,performance,reaction,Solid,catalysts,widely,used,production,various,high,value,added,industrially,important,chemicals,Although,compounds,modify,vacancy,site,has,been,extensively,studied,functionalized,modified,polyoxometalates,POMs,rarely,reported,In,this,work,two,were,synthesized,successfully,through,covalently,grafting,different,groups,cluster,respectively,Com,was,achieved,by,surface,situ,oxidation,while,Strong,Br,nsted,demonstrated,methods,including,potentiometric,titration,pyridine,adsorption,studies,oxides,nuclear,magnetic,resonance,NMR,systematic,investigation,relationship,among,structures,electron,density,carried,out,theory,DFT,calculation,experimental,results,which,revealed,that,modification,decreased,promoted,release,H+,When,applied,HAA,MF,cyclohexanone,exhibited,better,conversion,monocyclic,fuel,precursors,1a,yield,selectivity,than,attributed,strong,intramolecular,hydrogen,bonding,interactions,between,neighboring,Finally,also,showed,excellent,activity,several,aldehydes,ketones,acetone,methoxybenzaldehyde,This,opens,new,pathway,design,fabrication,novel,solid

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