CO oxidative coupling to dimethyl oxalate(DMO)is the most crucial step in coal to ethylene glycol.Pd-based supported catalysts have been verified effective for generating DMO,but concomitant generation of dimethyl carbonate(DMC)is always unavoidable.It is generally accepted that Pd(0)is the active spe-cies for producing DMO,while Pd(Ⅱ)for DMC.However,density functional theory calculations have pro-posed that the selectivity to DMO or DMC highly depends on the space state of Pd species rather than its oxidative state.It is thus urgently desired to develop high-efficient catalysts with well-defined structure,and further to elucidate the structure-performance relationship.In this work,HKUST-1 with unique structure of paired-Cu(Ⅱ)centers was chosen as ideal support to construct the catalysts with respective paired-Pd(Ⅱ)centers and isolated-Pd(Ⅱ)centers via in situ Pd species doping.In despite of featuring Pdδ+(δ≈2)oxidation state,the synthesized paired-Pd(Ⅱ)/HKUST-1 catalyst still exhibited DMO as dominant product(90.8％of DMO selectivity).For isolated-Pd(ll)/HKUST-1 catalyst,however,the main product was DMC(84.8％of DMC selectivity).Based on catalyst characterizations,the structures of paired-Pd(Ⅱ)centers and isolated-Pd(Ⅱ)centers were determined.DMO was generated from the coupling of adja-cent *COOCH3 intermediates adsorbed on paired-Pd(Ⅱ)centers,while DMC was produced from the reac-tion between methyl nitrite and the *COOCH3 intermediates formed on isolated-Pd(Ⅱ)centers.Current work is the first MOFs-based catalyst with well-defined structure being applied in CO oxidative coupling reaction,which not only sheds light on the structure-performance relationship,but also inspires the potential of using MOFs as tunable platform to design high-efficient catalysts in heterogeneous catalysis.

State Key Laboratory of Structural Chemistry,Fujian Institute of Research on the Structure of Matter,Chinese Academy of Sciences,Fuzhou 350002,Fujian,China;School of Chemistry&Chemical Engineering,Shandong University of Technology,Zibo 255049,Shandong,China;School of Chemistry and Chemical Engineering,Liaocheng University,Liaocheng 252000,Shandong,China

[1]Hong-Zi Tan;Zhe-Ning Chen;Kai-Qiang Jing;Jing Sun;Yu-Ping Xu;Ning-Ning Zhang;Zhong-Ning Xu;Guo-Cong Guo-.Paired-Pd(Ⅱ)centers embedded in HKUST-1 framework:Tuning the selectivity from dimethyl carbonate to dimethyl oxalate)[J].能源化学,2022(04):233-240

Paired,Pd,centers,embedded,HKUST,framework,Tuning,selectivity,from,dimethyl,carbonate,oxalate,oxidative,coupling,DMO,most,crucial,step,coal,ethylene,glycol,supported,catalysts,have,been,verified,effective,generating,but,concomitant,generation,DMC,always,unavoidable,It,generally,accepted,that,active,producing,while,However,density,functional,theory,calculations,posed,highly,depends,space,state,species,rather,than,its,thus,urgently,desired,develop,efficient,well,defined,further,elucidate,performance,relationship,In,this,unique,paired,was,chosen,ideal,construct,respective,isolated,via,situ,doping,despite,featuring,oxidation,synthesized,still,exhibited,dominant,product,For,however,main,Based,characterizations,structures,were,determined,generated,adja,COOCH3,intermediates,adsorbed,produced,between,nitrite,formed,Current,first,MOFs,being,applied,reaction,which,not,only,sheds,light,also,inspires,potential,using,tunable,platform,design,heterogeneous,catalysis

0.464999