Charge‐Assisted Ionic Hydrogen‐Bonded Organic Frameworks: Designable and Stabilized Multifunctional Materials

Abstract

Hydrogen‐bonded organic frameworks (HOFs) are a class of crystalline framework materials assembled by hydrogen bonds. HOFs have the advantages of high crystallinity, mild reaction conditions, good solution processability, and reproducibility. Coupled with the reversibility and flexibility of hydrogen bonds, HOFs can be assembled into a wide diversity of crystalline structures. Since the bonding energy of hydrogen bonds is lower than that of ligand and covalent bonds, the framework of HOFs is prone to collapse after desolventisation and the stability is not high, which limits the development and application of HOFs. In recent years, numerous stable and functional HOFs have been developed by π‐π stacking, highly interpenetrated networks, charge‐assisted, ligand‐bond‐assisted, molecular weaving, and covalent cross‐linking. Charge‐assisted ionic HOFs introduce electrostatic attraction into HOFs to improve stability while enriching structural diversity and functionality. In this paper, we review the development, the principles of rational design and assembly of charge‐assisted ionic HOFs, introduces the different building block construction modes of charge‐assisted ionic HOFs. Highlight the applications of charge‐assisted ionic HOFs in gas adsorption and separation, proton conduction, biological applications, etc., and prospects for the diverse design of charge‐assisted ionic HOFs structures and multifunctional applications.

Photoluminescent organic crystals and co-crystals

“…HOFs are more versatile due to their soft and adjustable pores, and together with other applications, have been utilized for the development of luminescent hosts. 160–164 H. Wang et al utilized the tetrahedrally functionalized AIE skeleton of TPE-tetra(amidinium) ions TPE 4+ for the development of periodic porous and fluorescent HOFs with a range of dicarboxylic acids including 2TP, 2BPY, 2BPH and 2TPh. Interestingly, the resultant HOFs were blue emitting with finely tuned emission wavelengths ranging between 453–487 nm and quantum yields of 4.6–3.6%.…”

Arylsulfonate Ionic Hydrogen-Bonded Organic Frameworks Enable Highly Stable and Superprotonic Conductivity for Enhancing Direct Methanol Fuel Cells

“…The abundant hydrogen bonding in the structure provides unique transport paths for the protons. Meanwhile, the acid–base organic molecules in the iHOFs as proton carriers or proton sources to transport protons efficiently, − which may obtain materials with superprotonic conductivity.…”

“…The stabilization of PEMs not only ensures the sustained and efficient transfer of protons but also enhances the longevity of battery operation . However, hydrogen bonds, being highly reversible and weak interactions, make HOFs unstable and hinder their further development in PEMs. − We attempt to enhance the stability by introducing π–π stacking, charge-assisted hydrogen bonding, constructing structural interpenetrating networks, etc. ,− Doping HOFs with excellent performance into proton-conducting polymers can greatly improve the continuity of the proton transport channel, leading to the development of PEMs with excellent performance. , Moreover, HOFs have good solution processability and easy healing and regeneration, facilitating the preparation of composite membranes; and they are very compatible with polymers, which avoids the formation of interinterfacial defects to a certain extent. ,,− This will broaden the scope of the fabrication of solid-state proton conductive membranes. Until now, iHOFs with superprotonic conductivity and superior stability have rarely been investigated.…”