A Series of Layered Assemblies of Hydrogen-Bonded, Hexagonal Networks of C₃-Symmetric π-Conjugated Molecules: A Potential Motif of Porous Organic Materials

Abstract

Hydrogen-bonded porous organic crystals are promising candidates for functional organic materials due to their easy construction and flexibility arising from reversible bond formation-dissociation. However, it still remains challenging to form porous materials with void spaces that are well-controlled in size, shape, and multiplicity because even well-designed porous frameworks often fail to generate pores within the crystal due to unexpected disruption of hydrogen bonding networks or interpenetration of the frameworks. Herein, we demonstrate that a series of C3-symmetric π-conjugated planar molecules (Tp, T12, T18, and Ex) with three 4,4'-dicarboxy-o-terphenyl moieties in their periphery can form robust hydrogen-bonded hexagonal networks (H-HexNets) with dual or triple pores and that the H-HexNets stack without interpenetration to yield a layered assembly of H-HexNet (LA-H-HexNet) with accessible volumes up to 59%. Specifically, LA-H-HexNets of Tp and T12 exhibit high crystallinity and permanent porosity after desolvation (activation): SABET = 788 and 557 m(2) g(-1), respectively, based on CO2 sorption at 195 K. We believe that the present design principle can be applied to construct a wide range of two-dimensional noncovalent organic frameworks (2D-nCOFs) and create a pathway to the development of a new class of highly porous functional materials.

Porous Molecular Solids and Liquids

“…Based on such analyses, CC3 would be predicted from its energy–structure landscape to be a robust tecton, 62 whereas CC1 would not. 129 More recently, the CSP approach was extended to extrinsically porous molecules, 68,138 such as the hydrogen-bonding frameworks developed by Mastalerz. 30 We showed that the energy–structure landscapes for such molecules can be complex: for example, a trigonal benzimidazolone was found to have at least four stable porous polymorphs with predicted densities in the broad range 0.4–1.25 g cm –3 and predicted surface areas ranging from 442 to 3230 m 2 g –1 .…”

Design of a Peripheral Building Block for H-Bonded Dendritic Frameworks and Analysis of the Void Space in the Bulk Dendrimers

“…Previously, the development of porous materials for CO 2 adsorption focused mostly on the design of new metal–organic frameworks (MOFs) 38–42 , hydrogen-bonded organic frameworks (HOFs) 43–49 , covalent–organic frameworks (COFs) 50–55 , and polymer organic frameworks (POFs) 56–59 . MOFs and HOFs, also known as self-assembled frameworks, were studied using single crystal X-ray analysis and then the available void space could be observed at the atomic level; many of them possess high surface areas and porosity and thus show a remarkable CO 2 sorption ability.…”

On‐Surface Self‐Assembly of a C3‐Symmetric π‐Conjugated Molecule Family Studied by STM: Two‐Dimensional Nanoporous Frameworks

“…Compounds Tp , T12 , T18 , and Ex were synthesized according to reported methods . STM experiments were performed with a NanoscopeIIIa (Veeco Metrology, USA) instrument with mechanically formed Pt/Ir (80/20) tips.…”

“…On this basis, recently, a series of C 3 ‐symmetric π‐conjugated planar molecules ( Tp , T12 , T18 , and Ex ; Scheme ) were synthesized to provide new ideas for advanced materials . The central cores of these molecules are designed with different side lengths; this is the main difference between the four molecules.…”