Single-atom catalysts have been applied in many processes recently.The difference of their kinetic behavior compared to the traditional heterogeneous catalysts has not been extensively discussed yet.Herein a complete ...Single-atom catalysts have been applied in many processes recently.The difference of their kinetic behavior compared to the traditional heterogeneous catalysts has not been extensively discussed yet.Herein a complete catalytic cycle of CH4 combustion assuming to be confined at isolated single sites of the Co3O4(110)surface is computationally compared with that on multi sites.The macroscopic kinetic behaviors of CH4 combustion on Co3O4(110)is systematically and quantitatively compared between those on the single site and multi sites utilizing kinetic Monte Carlo simulations upon the energetic information from the PBE+U calculation and statistic mechanics.The key factors governing the kinetics of CH4 combustion are disclosed for both the catalytic cycles respectively following the single-site and multi-site mechanisms.It is found that cooperation of multi active sites can promote the activity of complete CH4 combustions substantially in comparison to separated single-site catalyst whereas the confinement of active sites could regulate the selectivity of CH4 oxidation.The quantitative understanding of catalytic mechanism paves the way to improve the activity and selectivity for CH4 oxidation.展开更多
Three new cobalt complexes, {[Co5（tci）2（bimb）3（μ3-O）2（H2O）2]·3DMF·4H2O}n（1）, {[Co3（tci）2（bib）]·2DMF·2H2O}n （2） and {[Co（Htci）（bpea）0.5]-H2O}n （3） （H3tci = tris（2-carboxyet...Three new cobalt complexes, {[Co5（tci）2（bimb）3（μ3-O）2（H2O）2]·3DMF·4H2O}n（1）, {[Co3（tci）2（bib）]·2DMF·2H2O}n （2） and {[Co（Htci）（bpea）0.5]-H2O}n （3） （H3tci = tris（2-carboxyethyl）isocyanurate, bimb = 4,4＇-bis（imidazol-l-yl）biphenyl, bib = 1,4-bis（imidazol-l-yl）benzene, bpea = 1,2-bis（4-pyridyl）ethane, DMF = N,N＇-dimethylformamide）, have been successfully synthesized through the assembly of Co（If） ions, H3tci and different N-donor ligands, respectively. All complexes were structurally characterized by single crystal X-ray diffraction, elemental analyses, IR spectra, thermogravimetric （TG） analyses and X-ray powder diffraction （XRPD）. Complex 1 exhibits a 3D three-fold parallel interpenetrated 3D · 3D structure with （65.8） CdSO4 topology. Complex 2 is built from [Co3（μ/2-Ocarboxyl）2（CO2）4] clusters and linear bib ligands, displaying a two-fold par- allel interpenetrated （3,8）-connected （4^3）2（4^6.6^18·8^4） topology, while complex 3 is a 3D pillar-layered structure involving an in- finite -Co-（μ2-Ocarboxyl）（CO2）-Co-chain. The diverse structures of the three complexes indicate that the skeletons of different N-donor ligands play an important role in the assembly of such different frameworks. In addition, magnetic investigation indi- cates that besides spin-orbit coupling of Co（II） ions, there exist antiferromagnetic exchange interactions in Co5 and Co3 clus- ters of 1 and 2, respectively.展开更多
文摘Single-atom catalysts have been applied in many processes recently.The difference of their kinetic behavior compared to the traditional heterogeneous catalysts has not been extensively discussed yet.Herein a complete catalytic cycle of CH4 combustion assuming to be confined at isolated single sites of the Co3O4(110)surface is computationally compared with that on multi sites.The macroscopic kinetic behaviors of CH4 combustion on Co3O4(110)is systematically and quantitatively compared between those on the single site and multi sites utilizing kinetic Monte Carlo simulations upon the energetic information from the PBE+U calculation and statistic mechanics.The key factors governing the kinetics of CH4 combustion are disclosed for both the catalytic cycles respectively following the single-site and multi-site mechanisms.It is found that cooperation of multi active sites can promote the activity of complete CH4 combustions substantially in comparison to separated single-site catalyst whereas the confinement of active sites could regulate the selectivity of CH4 oxidation.The quantitative understanding of catalytic mechanism paves the way to improve the activity and selectivity for CH4 oxidation.
基金supported by the National Natural Science Foundation of China(21031002,51073079 and 21003078)Natural Science Foundation of Tianjin,China(11JCYBJC04100)
文摘Three new cobalt complexes, {[Co5（tci）2（bimb）3（μ3-O）2（H2O）2]·3DMF·4H2O}n（1）, {[Co3（tci）2（bib）]·2DMF·2H2O}n （2） and {[Co（Htci）（bpea）0.5]-H2O}n （3） （H3tci = tris（2-carboxyethyl）isocyanurate, bimb = 4,4＇-bis（imidazol-l-yl）biphenyl, bib = 1,4-bis（imidazol-l-yl）benzene, bpea = 1,2-bis（4-pyridyl）ethane, DMF = N,N＇-dimethylformamide）, have been successfully synthesized through the assembly of Co（If） ions, H3tci and different N-donor ligands, respectively. All complexes were structurally characterized by single crystal X-ray diffraction, elemental analyses, IR spectra, thermogravimetric （TG） analyses and X-ray powder diffraction （XRPD）. Complex 1 exhibits a 3D three-fold parallel interpenetrated 3D · 3D structure with （65.8） CdSO4 topology. Complex 2 is built from [Co3（μ/2-Ocarboxyl）2（CO2）4] clusters and linear bib ligands, displaying a two-fold par- allel interpenetrated （3,8）-connected （4^3）2（4^6.6^18·8^4） topology, while complex 3 is a 3D pillar-layered structure involving an in- finite -Co-（μ2-Ocarboxyl）（CO2）-Co-chain. The diverse structures of the three complexes indicate that the skeletons of different N-donor ligands play an important role in the assembly of such different frameworks. In addition, magnetic investigation indi- cates that besides spin-orbit coupling of Co（II） ions, there exist antiferromagnetic exchange interactions in Co5 and Co3 clus- ters of 1 and 2, respectively.
