CFA-2 and CFA-3 (Coordination Framework Augsburg University-2 and -3); novel MOFs assembled from trinuclear Cu(i)/Ag(i) secondary building units and 3,3′,5,5′-tetraphenyl-bipyrazolate ligands

Abstract

The syntheses of H₂-phbpz, [Cu₂(phbpz)]·2DEF·MeOH (CFA-2) and [Ag₂(phbpz)] (CFA-3) (H₂-phbpz = 3,3′,5,5′-tetraphenyl-1H,1′H-4,4′-bipyrazole) compounds and their crystal structures are described. The Cu(I) containing metal–organic framework CFA-2 crystallizes in the tetragonal crystal system, within space group I4₁/a (no. 88) and the following unit cell parameters: a = 30.835(14), c = 29.306(7) Å, V = 27 865(19) ų. CFA-2 features a flexible 3-D three-connected two-fold interpenetrated porous structure constructed of triangular Cu(I) subunits. Upon exposure to different kinds of liquids (MeOH, EtOH, DMF, DEF) CFA-2 shows pronounced breathing effects. CFA-3 crystallizes in the monoclinic crystal system, within space group P2₁/c (no. 14) and the following unit cell parameters: a = 16.3399(3), b = 32.7506(4), c = 16.2624(3) Å, β = 107.382(2)°, V = 8305.3(2) ų. In contrast to the former compound, CFA-3 features a layered 2-D three-connected structure constructed from triangular Ag(I) subunits. Both compounds are characterized by elemental and thermogravimetric analyses, single crystal structure analysis and X-ray powder diffraction, FTIR- and fluorescence spectroscopy. Preliminary results on oxygen activation in CFA-2 are presented and potential improvements in terms of framework robustness and catalytic efficiency are discussed.