A composite metal-organic frameworks(MOFs)structure,designated as Co-hmta@La-salen,was synthesized through coordination interactions between a one-dimensional lanthanum MOFs(La-salen)with high density of uncoordinated...A composite metal-organic frameworks(MOFs)structure,designated as Co-hmta@La-salen,was synthesized through coordination interactions between a one-dimensional lanthanum MOFs(La-salen)with high density of uncoordinated imine(-CH=N-)groups and a cobalt-based MOFs(Co-hmta)structure prepared using hydrogen bonding stacking with hexamethylenetetramine(hmta)as the organic ligand.Subsequently,the Co-hmta@La-salen composite was chosen as a template for the pyrolysis process to synthesize a La(OH)_(3)supported metallic Co catalyst incorporating carbon-nitrogen(Co/La(OH)_(3)-CNhmta)catalyst.The catalytic results show that Co/La(OH)_(3)-CN-hmta(54%and 46%selectivity for aniline and N-phenylbenzylamine,respectively)displays superior cascade performance compared to classic Co/La(OH)_(3)-CN-nit catalyst(69%and 31%selectivity for aniline and N-phenylbenzylamine,respectively).Moreover,the kinetic test results indicate that N-alkylation is the rate-limiting step of the overall cascade reaction.The Co/La(OH)_(3)-CN-hmta catalyst can be separated from the reaction system using a magnet,and it also exhibits good cyclic stability.All of these suggest that the“MOFs plus MOFs via coordination”templating method can be employed as an efficient strategy for the preparation of supported catalysts.展开更多
Defect engineering in metal organic frameworks(MOFs)has captured significant attention in the field of photocatalysis.A series of UiO-66(Ce)(UiO=University of Oslo)MOFs with different contents of missing-linker defect...Defect engineering in metal organic frameworks(MOFs)has captured significant attention in the field of photocatalysis.A series of UiO-66(Ce)(UiO=University of Oslo)MOFs with different contents of missing-linker defects have been developed for the photocatalytic selective oxidation of benzylamine(BA)and thioanisole(TA)under visible light.The introduction of missing-linker defects promotes the formation of unsaturated Ce sites with a high Ce3+content.It also generates a high concentration of oxygen vacancies.In situ Fourier transform infrared spectroscopy(FTIR)results revealed that BA and TA molecules were activated on coordinatively unsaturated Ce sites via the H-N…Ce and the C-S…Ce interactions,respectively.Simulated in situ electron paramagnetic resonance(EPR)data indicate that O_(2) activation and reduction occur at coordinatively unsaturated Ce^(3+)sites to form·O_(2)^(-).This is accelerated by the Ce^(3+)/Ce^(4+)redox cycle associated with the photogenerated electrons.The corresponding photogenerated holes are involved in the deprotonation of the activated BA and TA.The most active sample exhibits 98.4%and 95.5%conversion rates for BA and TA oxidation.Mechanisms for the molecular activation are proposed at the molecular level.展开更多
基金Project supported by the Natural Science Foundation of Jiangsu Province (BK20210066)Natural Science Foundation of Heilongjiang Province (ZD2022E007).
文摘A composite metal-organic frameworks(MOFs)structure,designated as Co-hmta@La-salen,was synthesized through coordination interactions between a one-dimensional lanthanum MOFs(La-salen)with high density of uncoordinated imine(-CH=N-)groups and a cobalt-based MOFs(Co-hmta)structure prepared using hydrogen bonding stacking with hexamethylenetetramine(hmta)as the organic ligand.Subsequently,the Co-hmta@La-salen composite was chosen as a template for the pyrolysis process to synthesize a La(OH)_(3)supported metallic Co catalyst incorporating carbon-nitrogen(Co/La(OH)_(3)-CNhmta)catalyst.The catalytic results show that Co/La(OH)_(3)-CN-hmta(54%and 46%selectivity for aniline and N-phenylbenzylamine,respectively)displays superior cascade performance compared to classic Co/La(OH)_(3)-CN-nit catalyst(69%and 31%selectivity for aniline and N-phenylbenzylamine,respectively).Moreover,the kinetic test results indicate that N-alkylation is the rate-limiting step of the overall cascade reaction.The Co/La(OH)_(3)-CN-hmta catalyst can be separated from the reaction system using a magnet,and it also exhibits good cyclic stability.All of these suggest that the“MOFs plus MOFs via coordination”templating method can be employed as an efficient strategy for the preparation of supported catalysts.
基金supported by the National Natural Science Foundation of China(Nos.22272026 and 22272028)the 111 Project(No.D16008)Jinhong Bi thanks the Youth Talent Support Program of Fujian Province(No.00387077).
文摘Defect engineering in metal organic frameworks(MOFs)has captured significant attention in the field of photocatalysis.A series of UiO-66(Ce)(UiO=University of Oslo)MOFs with different contents of missing-linker defects have been developed for the photocatalytic selective oxidation of benzylamine(BA)and thioanisole(TA)under visible light.The introduction of missing-linker defects promotes the formation of unsaturated Ce sites with a high Ce3+content.It also generates a high concentration of oxygen vacancies.In situ Fourier transform infrared spectroscopy(FTIR)results revealed that BA and TA molecules were activated on coordinatively unsaturated Ce sites via the H-N…Ce and the C-S…Ce interactions,respectively.Simulated in situ electron paramagnetic resonance(EPR)data indicate that O_(2) activation and reduction occur at coordinatively unsaturated Ce^(3+)sites to form·O_(2)^(-).This is accelerated by the Ce^(3+)/Ce^(4+)redox cycle associated with the photogenerated electrons.The corresponding photogenerated holes are involved in the deprotonation of the activated BA and TA.The most active sample exhibits 98.4%and 95.5%conversion rates for BA and TA oxidation.Mechanisms for the molecular activation are proposed at the molecular level.
