Photocatalytic oxidation coupling of amines represents a green and cost-effective method for the synthesis of highly value-added imines under visible light irradiation.However,the catalytic efficiency was severely lim...Photocatalytic oxidation coupling of amines represents a green and cost-effective method for the synthesis of highly value-added imines under visible light irradiation.However,the catalytic efficiency was severely limited by poor visible light response and easy recombination of photogenerated charge carriers.Herein,we report a g-CgN_(4)/α-Bi_(2)O_(3)Z-scheme heterojunction via electrostatic self-assembly of g-C_(3)N_(4)nanosheets and oxygen-va-cancy-rich aα-Bi_(2)O_(3)microsphere for visible-light driven oxidative coupling of amines to imines in H_(2)0 as green solvent at room temperature.Amines with diverse functional groups were efficiently converted into the corre-sponding imines in good to excellent yields.Impressively,this photocatalytic protocol is applicable for the challenging hetero-coupling of two structurally different amines to construct complicated asymmetric imines,which is the first report of photocatalytic hetero-coupling of amines to imines to our knowledge.Furthermore,the Z-scheme heterojunction also demonstrated high stability and could be readily separated and reused without obvious decay in activity and selectivity.Comprehensive characterizations and control experiments reveal the construction of Z-scheme heterojunction with intimate interface between g-CgN4 and a-Bi_(2)O_(3)greatly boosts the transfer and separation of photogenerated charge carries and enhances the redox capability.Meanwhile,the surface oxygen vacancies in a-Biz_(2)O_(3)also benefits the separation of photogenerated charge carriers and acti-vation of reactants.These jointly contributed to an enhanced photocatalytic performance for oxidative coupling of amines to imines.展开更多
A series of h-BN based composites with Yb_4Si_2O_7N_2 as a secondary phase were successfully synthesized by an in situ reaction hot pressing method. It was found that the relative density and room-temperature mechanic...A series of h-BN based composites with Yb_4Si_2O_7N_2 as a secondary phase were successfully synthesized by an in situ reaction hot pressing method. It was found that the relative density and room-temperature mechanical properties monotonically increased with increasing the content of Yb_4Si_2O_7N_2 from 20 to 50 vol%. When 50 vol% Yb_4Si_2O_7N_2 was introduced, the relative density of the composite reached 98.75%, and its flexural strength, compressive strength, fracture toughness, and hardness reached 338±10 MPa, 803±49 MPa, 2.06±0.06 MPa·m1/2, and 2.69±0.10 GPa, respectively. The strengthening effect of Yb_4Si_2O_7N_2 was mainly attributed to its high modulus and high hardness. Fine microstructure was also advantageous to strength and could lead to more tortuous crack propagation paths and then improve the fracture toughness of the composites simultaneously. Meanwhile, the composites maintained good machinability.展开更多
基金supported by the National Natural Science Foundation of China(No.22078350)the Natural Science Foundation of Shandong Province(ZR2020KB016)Shandong Energy Institute Fund(Grant no.SEII202138).
文摘Photocatalytic oxidation coupling of amines represents a green and cost-effective method for the synthesis of highly value-added imines under visible light irradiation.However,the catalytic efficiency was severely limited by poor visible light response and easy recombination of photogenerated charge carriers.Herein,we report a g-CgN_(4)/α-Bi_(2)O_(3)Z-scheme heterojunction via electrostatic self-assembly of g-C_(3)N_(4)nanosheets and oxygen-va-cancy-rich aα-Bi_(2)O_(3)microsphere for visible-light driven oxidative coupling of amines to imines in H_(2)0 as green solvent at room temperature.Amines with diverse functional groups were efficiently converted into the corre-sponding imines in good to excellent yields.Impressively,this photocatalytic protocol is applicable for the challenging hetero-coupling of two structurally different amines to construct complicated asymmetric imines,which is the first report of photocatalytic hetero-coupling of amines to imines to our knowledge.Furthermore,the Z-scheme heterojunction also demonstrated high stability and could be readily separated and reused without obvious decay in activity and selectivity.Comprehensive characterizations and control experiments reveal the construction of Z-scheme heterojunction with intimate interface between g-CgN4 and a-Bi_(2)O_(3)greatly boosts the transfer and separation of photogenerated charge carries and enhances the redox capability.Meanwhile,the surface oxygen vacancies in a-Biz_(2)O_(3)also benefits the separation of photogenerated charge carriers and acti-vation of reactants.These jointly contributed to an enhanced photocatalytic performance for oxidative coupling of amines to imines.
基金supported by the National Natural Science Foundation of China under Grant Nos.50802099 and 51072201
文摘A series of h-BN based composites with Yb_4Si_2O_7N_2 as a secondary phase were successfully synthesized by an in situ reaction hot pressing method. It was found that the relative density and room-temperature mechanical properties monotonically increased with increasing the content of Yb_4Si_2O_7N_2 from 20 to 50 vol%. When 50 vol% Yb_4Si_2O_7N_2 was introduced, the relative density of the composite reached 98.75%, and its flexural strength, compressive strength, fracture toughness, and hardness reached 338±10 MPa, 803±49 MPa, 2.06±0.06 MPa·m1/2, and 2.69±0.10 GPa, respectively. The strengthening effect of Yb_4Si_2O_7N_2 was mainly attributed to its high modulus and high hardness. Fine microstructure was also advantageous to strength and could lead to more tortuous crack propagation paths and then improve the fracture toughness of the composites simultaneously. Meanwhile, the composites maintained good machinability.
