Covalent organic frameworks (COFs) are porous crystalline networks made from organic building blocks. They have potential applications, e.g., in gas storage and separation, catalysis, or sensing. The pore size of COFs is an important property that needs to be tailored for different applications.

Xiao Feng, Beijing Institute of Technology, China, and colleagues have prepared a series of COFs with record pore aperture sizes of 7.7–10.0 nm. The largest previously known pore size in a COF had been 5.8 nm, and the largest metal–organic framework (MOF) pore aperture is 8.5 nm.

The team prepared three COFs, called TDCOF-1, TDCOF-2, and TDCOF-3 via co-condensation of the amine building block 4′,4”’,4””’-(1,3,5-triazine-2,4,6-triyl)tris([1,1′-biphenyl]-4-amine) (TBA-NH₂) with the aldehydes 4,4′-((2,3-dimethoxy-1,4-phenylene)bis(ethyne-2,1-diyl))dibenzaldehyde (DMBD-CHO), 4,4′-(1,4-phenylenebis(ethyne-2,1-diyl))dibenzaldehyde (BD-CHO), or 4,4′-((((2,3-dimethoxy-1,4-phenylene)bis(ethyne-2,1-diyl))bis(4,1-phenylene))bis(ethyne-2,1-diyl))dibenzaldehyde (BDMBD-CHO), respectively, under solvothermal conditions.

All three COFs are imine-linked, hexagonal, mesoporous frameworks. The materials show high crystallinity, permanent porosity, and high thermal and chemical stabilities.

• Covalent Organic Frameworks with Record Pore Apertures,
  Zhenjie Mu, Yuhao Zhu, Bixiao Li, Anwang Dong, Bo Wang, Xiao Feng,
  J. Am. Chem. Soc. 2022.
  https://doi.org/10.1021/jacs.2c00584