Recent Applications of Multifunctional Boron Imidazolate Framework Materials

ConspectusBoron imidazolate frameworks (BIFs) were first reported as a kind of zeolite-like metal–organic frameworks (MOFs). Zeolites are crystalline materials with porous properties and significant commercial values. In recent decades, the rapid development of MOFs, which are formed by coordinate bonds between metal ions or clusters with organic ligands, offers great opportunities for the rational design of new crystalline materials. Therefore, the zeolite-like MOFs with zeolitic topologies have become a hot topic in both chemistry and materials research, due to their periodic network structures, tunable pore size, and tailorable microenvironments.In 2009, Jian Zhang and coauthors first introduced the rational design and synthesis of a family of zeolitic boron imidazolate frameworks (BIFs) by the cross-link of presynthesized boron imidazolate ligands (B(im)4– or BH(im)3–) and monovalent tetrahedral metal centers. Since then, BIFs have been continuously explored as a new type of materials with promising applications due to their unique advantages of ultralightweight, zeolitic topologies, two-step synthesis, various metal centers, controllable tetrahedral and tripodal boron imidazolate ligands. BIFs also can be regarded as a unique family of materials that lie between MOFs and covalent organic frameworks (COFs) because of the coexistence of covalent (B–N) and coordination bonds (M–N). However, most of the initially obtained traditional zeolite-like BIFs have relatively dense structures, which is due to the shorter B–N distance (about 1.5 Å) compared to larger metal–ligand distances in MOF (usually about 2.0 Å). Recent reports have shown that the introduction of O-donor carboxylate ligands into the N-donor B-im-M system creates a new synthetic advancement as well as a variety of functional structures. Furthermore, both tetrahedral B(im)4– and tripodal BH(im)3– ligands can be readily synthesized prior to solvothermal synthesis. Take the advantages of the controllability of boron imidazolate ligands, the synthesized BIF structures break through the limitation of the traditional four-connected zeolite topology and achieve the diversity of materials, such as interrupted zeolite type frameworks with open architecture and pore-space-partition type zeolite with functional pore surfaces. Such synthetic and pore engineering further expanded the potential applications of BIFs in gas adsorption and separation, solid-state photoluminescence, and mechanochromic photoluminescence. Moreover, catalysis is one of the most promising applications of MOFs and has attracted widespread interest. It faces an even more significant challenge, which is the limited stability in harsh reaction conditions. The B–N covalent bonds and M–N coordination bonds within the framework provide good stability and reducibility for BIFs.In this Account, we aim to shed light on the recent advancements in the development of functional structures based on BIFs, and their diverse applications in multiple domains, including gas adsorption and separation, solid-state photoluminescence, and mechanochromic photoluminescence, photocatalysis, and electrocatalysis. We firmly believe that BIFs still hold great potential for further development in structural design, functional regulation, and a wide range of applications, making them an attractive field for ongoing research.