CFA-4 – a fluorinated metal–organic framework with exchangeable interchannel cations

Abstract

The syntheses and crystal structures of the fluorinated linker 1,4-bis(3,5-bis(trifluoromethyl)-1H-pyrazole-4-yl)benzene (H₂-tfpb; 1) and the novel metal–organic framework family M[CFA-4] (Coordination Framework Augsburg University-4), M[Cu₅(tfpb)₃] (M = Cu(I), K, Cs, Ca(0.5)), are described. The ligand 1 is fully characterized by single crystal X-ray diffraction, photoluminescence-, NMR-, IR spectroscopy, and mass spectrometry. The copper(I)-containing MOF crystallizes in the hexagonal crystal system within the chiral space group P6₃22 (no. 182) and the unit cell parameters are as follows: a = 23.630(5) Å, c = 41.390(5) Å, V = 20 015(6) ų. M[CFA-4] features a porous 3-D structure constructed from pentanuclear copper(I) secondary building units {Cu^I₅(pz)₆}⁻ (pz = pyrazolate). Cu(I)[CFA-4] is fully characterized by synchrotron single crystal X-ray diffraction, thermogravimetric analysis, variable temperature powder X-ray diffraction, IR spectroscopy, photoluminescence and gas sorption measurements. Moreover, thermal stability and gas sorption properties of K[CFA-4] and Cu(I)[CFA-4] are compared.