Two-Dimensional Molecular Porous Networks Formed by Trimesic Acid and 4,4'-Bis(4-pyridyl)biphenyl on Au(111) through Hierarchical Hydrogen Bonds: Structural Systematics and Control of Nanopore Size and Shape

摘要

Two-dimensional (2D) molecular porous networks (MPNs) self-assembled on surfaces are of great interest due to their potential applications in nanoscience. Conventionally, the assembled molecules are held together by non-covalent interactions, among which the hydrogen bond (HB) is frequently adopted for structural controllability owing to its desirable bonding strength, selectivity, and directionality. This strategy has been utilized in both uni-and bimolecu-lar systems Generally speaking, hydrogen bonds of similar bond strength are less versatile than hierarchical ones in tuning the assembled structures. In nature, hierarchical hydrogen-bond systems with disparate bonding capabilities and strengths are widely adopted by biosystems such as DNA and bioactive structures which consist of only limited building blocks. Researchers have utilized metal coordination or hydrogen bonds to form various porous networks on surfaces. Controls of the network pattern and the resulting pore size and shape can be achieved by tuning parameters such as ligand chain lengths or molecular backbones, surface coverage and substrate temperature.