Porosity Properties of the Conformers of Sodalite-like Zeolitic Imidazolate Frameworks

Abstract

The conformational isomers of zeolitic imidazolate frameworks (ZIFs) can have their own unique porosity and structural stability. We report that a new sodalite-like ZIF (termed β-ZIF-65(Zn)) is polymorphous with as the existing ZIF-65(Zn) (Zn(nIm)₂, nIm = 2-nitroimidazolate) but has a different linker conformation in the six-membered rings of sodalite cages. This conformational isomerism leads to distinctive permanent porosity for each conformer, which has been verified by gas adsorption measurements. In addition, variable-temperature X-ray diffraction analyses indicate that β-ZIF-65(Zn) is more resistant to displacive phase transitions than ZIF-65(Zn). The activated β-ZIF-65(Zn) conformer adsorbs 2.8 times more benzene than the activated ZIF-65(Zn) at P/ P₀ = 0.3 and 298 K. This work suggests that other types of ZIF conformers can be discovered.