Theoretical Investigation of the Topology of Spiroborate‐Linked Ionic Covalent Organic Frameworks (ICOFs)

Abstract

A novel type of ionic covalent organic framework (ICOF) with a spiroborate linkage has been recently designed and synthesized by Zhang and co‐workers (Ionic Covalent Organic Frameworks with Spiroborate Linkage, Angew. Chem. Int. Ed. 2016, 55, 1737–1741). The spiroborate‐linked ICOFs exhibit high Brunauer–Emmett–Teller (BET) surface areas and significant amounts of H2 and CH4 uptakes, combined with excellent thermal and chemical stabilities. Inspired by the novel properties of ICOFs, with the aim of gaining better understanding of the structure of such spiroborate‐linked ICOFs, a series of potential 3D network configurations of ICOFs connected with tetrahedral [BO4]− nodes were proposed, assuming the [BO4]− node in spiroborate segments takes a tetrahedral configuration. These ICOFs, in terms of 2D and 3D topology through torsional energy of the [BO4]− fragment, pore‐size distribution, total energy of the framework, and gas adsorption properties were compared and systematically investigated by density functional theory calculations, molecular mechanics, and well‐established Grand canonical Monte Carlo simulations. The results indicate that spiroborate‐linked ICOFs are likely a mixture of various topologies. Among these architectures, the five‐fold interpenetrating model shows the lowest energy and reasonable gas uptakes, therefore, it is considered to be the most possible structure. More importantly, the five‐fold interpenetrating model, showing high CH4 uptakes compared with several classic porous materials, represents a promising CH4 storage material.

Structure–performance correlation guided applications of covalent organic frameworks

“…In addition, ionic COF (iCOF), fabricated by the introduction of ionic components into the framework structure, endows COFs with favorable adsorption capacity for gas molecules and metal ions [279,280]. Controlling the amount of surface charge in iCOFs may change the binding capacity of guests (such as chromium(VI)) [281].…”

Covalent Organic Frameworks with Ionic Liquid-Moieties (ILCOFs): Structures, Synthesis, and CO2 Conversion

“…Owing to the high porosity, flexible building blocks, and charged skeleton, CD-COFs show great potential in the fields of ion conduction and gas separation. Subsequently, Li and Zhang et al [ 68 ] theoretically investigated the topology of spiroborate-linked ILCOFs.…”

Rational Fabrication of Ionic Covalent Organic Frameworks for Chemical Analysis Applications

“…By combining the advantages of porous ionic polymers (PiPs) and COFs, iCOFs not only retain the design concept of COFs with unique atomic periodicity and backbone porosity but also involve groups with opposite charges in the skeletons of iCOFs through electrostatic interactions or ion exchange [ 25 ]. These features benefit the wide applications of iCOFs in ion conduction, catalysis, energy storage, adsorption, and separation [ 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. More intriguingly, the permanent porosity, precisely designable structure, and unique ionic sites endow iCOFs as good candidates for effective and selective extraction of tracing elements and matters.…”