A Brick-Wall Topological 2D Covalent Organic Framework Constructed from an H-Shaped "Two-in-One" Monomer

As an emerging class of porous crystalline material, covalent organic frameworks (COFs) have received considerable research interests in terms of exploring new architectures and functions. Herein, we developed an unprecedented "H-shaped" monomer, upon self-polycondensation, which facilely produced a benzoimidazole-based COF (H-BIm-COF) with a rarely reported brick-wall topology. H-BIm-COF displayed high crystallinity, nano-sized porosity, and high thermal and chemical stabilities. Interestingly, H-BIm-COF based membranes showed selective permeability towards different solvents, which related to the size and polarity of the guest molecule. Additionally, initial study suggested the COF displayed excellent rejection efficiency towards ionic dyes, for example chromium black T (99.7 %) and rhodamine B (97.3 %). This work provides insights into developing new topological COFs by designing monomers with new configurations.