Balancing Noncovalent Interactions in the Self-Assembly of Nonplanar Aromatic Carboxylic Acid MOF Linkers at the Solution/Solid Interface: HOPG vs Au(111)

Abstract

This study explores directed noncovalent bonding in the self-assembly of nonplanar aromatic carboxylic acids on gold and graphite surfaces. It is the first step in developing a new design strategy to create two-dimensional surface metal−organic frameworks (SURFMOFs). The acid molecules used are tetraphenylethene-based and are typically employed in the synthesis of three-dimensional (3D) MOF crystalline solids. They include tetraphenylethene tetracarboxylic acid, tetraphenylethene bisphenyl carboxylic acid, and tetraphenylethene tetrakis-phenyl carboxylic acid. The twodimensional structures formed from these molecules on highly ordered pyrolytic graphite (HOPG) and Au(111) are studied by scanning tunneling microscopy in a solution environment. The process of monolayer formation and final surface linker structures are found to be strongly dependent on the combination of the molecule and substrate used and are discussed in terms of intermolecular and molecule−substrate interactions, bonding geometry, and symmetry of the acid molecules. In the case of linker self-assembly on HOPG, the molecule−substrate interactions play a significant role in the resulting surface structure. When the acid molecules are adsorbed on Au(111), the intermolecular interactions tend to dominate over the weaker molecule−substrate bonding. Additionally, the interplay of π−π interactions and hydrogen bonding that directs the surface selfassembly on different supports can be modified by varying the linker concentration. This is particularly applicable for the case of the acid molecules adsorbing on the Au(111) substrate. Precise control over predesigned surface structures and orientation of the nonplanar aromatic carboxylic linkers open up an exciting prospect for manipulating the direction of SURFMOF growth in two dimensions and potentially in 3D.

Supramolecular Chemistry: Host–Guest Molecular Complexes

“…Thus, MOF was investigated a lot by different research groups due to its practical applicability in device fabrication such as photovoltaics, semiconductors, hydrogen storage, water purification, drug delivery, or sensor devices for detecting and removing environmental pollutants [ 59 , 60 ] such as the study of 2D MOF of thiolate copper coordination bonds under UHV conditions on Ag (111) and Cu (111) substrate. A room temperature study reveals similar trigonal topography and lattice parameters.…”

“…However, annealing generates two varying porous nanostructures on Cu (111) at ~150 °C. On Ag, (111) structural transformation observes up to ~300 °C) [ 56 , 57 ] or the exploration of aromatic carboxylic acids having directional noncovalent bonding on Au and HOPG substrate generating 2D MOF possessing intermolecular or molecule substrate interfaces, influenced by bonding formation or molecular arrangement [ 59 ], or the study of a low symmetric aromatic carboxylic acid possessing meta-carboxyl groups structured by pyridine derivatives [ 61 ]. Tha halogen-adatom structural transformation in 2D molecular grouping shows non-covalent interactions and catalytic responses on a metal substrate [ 62 ].…”

The self-assembly and pyridine regulation of a hydrogen-bonded dimeric building block formed by a low-symmetric aromatic carboxylic acid

“…19,20 In addition, symmetrically distributed aromatic tetracarboxylic acid molecules such as NN4A and H 4 ETTC have been proved to be able to form uniform Kagomé or quadrilateral networks, respectively. 21–23 In general, rigid planar aromatic molecules with symmetrically distributed carboxylic acid groups are usually able to assemble into an ordered network in a highly predictable fashion. Moreover, because symmetrical aromatic carboxylic acid molecules are easier to synthesize, the aromatic carboxylic acid molecules involved in current studies of self-assembly are usually symmetric.…”

Electron-Induced Modification of Self-Assembled Monolayers of Aromatic Carboxylic Acids

“…Compared to archetypical self-assembled monolayers (SAMs) with the thiolate docking group, 1,2 carboxylic-acid (CA) based SAMs, specifically those featuring aromatic backbones, have been investigated in detail only more recently. [3][4][5][6][7][8][9][10][11][12][13][14][15] These SAMs can be efficiently assembled from solution on a variety of substrates, including the coinage metals silver and copper. Silver, in particular, has turned out as beneficial for a flexible SAM design, owing to a comparatively weak interaction between the CA docking group and the substrate.…”

“…Compared with archetypical self-assembled monolayers (SAMs) with the thiolate docking group, , carboxylic acid (CA)-based SAMs, specifically those featuring aromatic backbones, have been investigated in detail only more recently. − These SAMs can be efficiently assembled from solution on a variety of substrates, including the coinage metals silver and copper. Silver, in particular, has turned out to be beneficial for a flexible SAM design, owing to a comparatively weak interaction between the CA docking group and the substrate. − ,,, Consequently, the molecular structure and intermolecular interactions become factors for self-assembly, dominating over molecule–substrate interactions, so that the structure and organization of a SAM can be flexibly tuned by the design of its constituents.…”