Charge-Assisted Hydrogen-Bonded Organic Frameworks: From Crystal Engineering to Multifunctional Materials

Crystalline porous materials formed through intermolecular interactions such as hydrogen bonding interactions and van der Waals forces are known as hydrogen-bonded organic frameworks (HOFs). As a type of HOFs, charge-assisted HOFs are composed of organic acids and bases jointly interacted through hydrogen bonding and electrostatic interactions. Charge-assisted HOFs show the advantages of high crystallinity, ease of processing, recyclability, and low toxicity. Moreover, the introduction of additional electrostatic interactions can enhance the binding energy of hydrogen bonds, which not only improves the stability of the framework but also endows the channels with unique charge-separation characteristics. This review highlights the important factors affecting the design and synthesis of charge-assisted HOFs, including the acidity and basicity of monomers, solvent effects, and the role of topology in guiding the design. Additionally, it briefly introduces the applications of charge-assisted HOFs in the fields of negative linear compressibility, proton conduction, atmospheric water harvesting, gas adsorption and separation, molecular rotors, optics, and biological applications. The challenges and future prospects in the design and synthesis of charge-assisted HOFs are also explored.