In on-surface synthesis,dimers are typically utilized to explore reaction mechanisms or as intermediates in the formation of final products.However,constructing the innovative nanostructures with dimers as building bl...In on-surface synthesis,dimers are typically utilized to explore reaction mechanisms or as intermediates in the formation of final products.However,constructing the innovative nanostructures with dimers as building blocks remains challenging.Here,using non-planar 2,2′,7,7′-tetrabromo-9,9′-biflurenyliden molecules,we have successfully synthesized dimeric covalent organic frameworks(COFs)on the Au(111)surface through a temperature-controlled cascade reaction.Notably,the H-H steric hindrance within precursors caused by double bonds leads to selective stepwise debromination during the thermal annealing,which promotes the dimerization through intermolecular Ullmann coupling and cyclodehydrogenation reaction to form COFs primarily constituted by dimer building blocks.Combining scanning tunneling microscopy/spectroscopy and density functional theory calculations,we have precisely confirmed the structural evolution and reaction mechanism.Furthermore,by introducing Ag adatoms to form C−Ag−C intermediates,we have successfully regulated the reaction path and synthesized one-dimensional nanoribbons with dimers as building blocks.This work not only validates the strategy of synthesizing dimeric nanostructures on different surfaces through cascade reactions induced by precursor design,but also enriches the research field of surface synthesis of COFs and nanoribbons.展开更多
基金supported by the National Natural Science Foundation of China(Nos.62271238,22372074,62301240)Yunnan Fundamental Research Projects(Nos.202201AT070078,202201BE070001-009 and 202301AW070017)+3 种基金the Major Basic Research Project of Science and Technology of Yunnan(202302AG050007)Yunnan Innovation Team of Graphene Mechanism Research and Application Industrialization(202305AS350017)Graphene Application and Engineering Research Center of Education Department of Yunnan Providence(KKPP202351001)Numerical computations were performed at Hefei Advanced Computing Center.
文摘In on-surface synthesis,dimers are typically utilized to explore reaction mechanisms or as intermediates in the formation of final products.However,constructing the innovative nanostructures with dimers as building blocks remains challenging.Here,using non-planar 2,2′,7,7′-tetrabromo-9,9′-biflurenyliden molecules,we have successfully synthesized dimeric covalent organic frameworks(COFs)on the Au(111)surface through a temperature-controlled cascade reaction.Notably,the H-H steric hindrance within precursors caused by double bonds leads to selective stepwise debromination during the thermal annealing,which promotes the dimerization through intermolecular Ullmann coupling and cyclodehydrogenation reaction to form COFs primarily constituted by dimer building blocks.Combining scanning tunneling microscopy/spectroscopy and density functional theory calculations,we have precisely confirmed the structural evolution and reaction mechanism.Furthermore,by introducing Ag adatoms to form C−Ag−C intermediates,we have successfully regulated the reaction path and synthesized one-dimensional nanoribbons with dimers as building blocks.This work not only validates the strategy of synthesizing dimeric nanostructures on different surfaces through cascade reactions induced by precursor design,but also enriches the research field of surface synthesis of COFs and nanoribbons.
