COF syntheses employed Schiff base reactions and self-condensation of boronic acid, as well as coupling between boronic acid and catechol 1, 7, 8, 9, 10. 7), developments in both solvothermal and on-surface syntheses have increased the diversity of COF structures, which are mainly composed of light elements (B, C, N, O, H). Since the seminal work on COF synthesis by Yaghi and co-workers in 2005 (ref. For the linear structure obtained with the pyrene-based precursor, the C 4Si 2 rings were converted into C 4Si pentagonal siloles by further annealing.Ĭovalent organic frameworks (COFs), as a large class of porous organic materials, have attracted intense research in the past few decades due to the great potential for applications in the fields of, for example, catalysis 1, 2, optoelectronics 3, 4 and gas storage and separation 5, 6. Each Si in a hexagonal C 4Si 2 ring was found to be covalently linked to one terminal Br atom. The subsequent deposition and annealing of a bromo-substituted polyaromatic hydrocarbon precursor (triphenylene or pyrene) on this surface led to the formation of the C 4Si 2-bridged networks, which were characterized by a combination of high-resolution scanning tunnelling microscopy and photoelectron spectroscopy supported by density functional theory calculations. Silicon atoms were first deposited on a Au(111) surface, forming a AuSi x film on annealing. Here we present the on-surface synthesis of one- and two-dimensional covalent organic frameworks whose backbones contain 1,4-disilabenzene (C 4Si 2) linkers. Silicon-doped graphene-based materials are known to exhibit exotic properties, yet conjugated organic materials with atomically precise Si substitution have remained difficult to prepare. Substituting carbon with silicon in organic molecules and materials has long been an attractive way to modify their electronic structure and properties.
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