Hydrogen-Bonded Organic Frameworks as a Tunable Platform for Functional Materials

As a novel class of porous crystalline materials, hydrogen-bonded organic frameworks (HOFs), self-assembled from organic or metal–organic building blocks through intermolecular hydrogen-bonding interactions, have attracted more and more attention. Over the past decade, a number of porous HOFs have been constructed through judicious selection of H-bonding motifs, which are further enforced by other weak intermolecular interactions such as π–π stacking and van der Waals forces and framework interpenetration. Since the H-bonds are weaker than coordinate and covalent bonds used for the construction of metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), HOFs have some unique features such as mild synthesis condition, solution processability, easy healing, and regeneration. These features enable HOFs to be a tunable platform for the construction of functional materials. Here, we review the H-bonding motifs used for constructing porous HOFs and highlight some of their applications, including gas separation and storage, chiral separation and structure determination, fluorescent sensing, heterogeneous catalysis, biological applications, proton conduction, photoluminescent materials, and membrane-based applications.