CFA-13 – a bifunctional perfluorinated metal–organic framework featuring active Cu(i) and Cu(ii) sites

Abstract

The synthesis and crystal structure of the mixed-valent perfluorinated metal–organic framework (Me₂NH₂)[CFA-13] (Coordination Framework Augsburg University-13), (Me₂NH₂)[Cu^I₃Cu^II₂(tfpc)₄] (H₂-tfpc = 3,5-bis(trifluoromethyl)-1H-pyrazole-4-carboxylic acid) is described. The copper-containing MOF crystallizes in the monoclinic crystal system within the space group P2₁/n (no. 14) and the unit cell parameters are as follows: a = 22.3887(19), b = 13.6888(8), c = 21.1804(13) Å, β = 90.495(3)°, V = 6491.0(8) ų. (Me₂NH₂)[CFA-13] features a porous 3-D structure constructed from two types of secondary building units (SBUs). Besides novel trinuclear [Cu^I₃(pz)₄]⁻ coordination units, the network also exhibits Cu(II) paddle-wheel SBUs. (Me₂NH₂)[CFA-13] is fully characterized by single crystal X-ray diffraction, thermogravimetric analysis, variable temperature powder X-ray diffraction, IR spectroscopy, photoluminescence, gas sorption measurements and pulse chemisorption experiments. M[CFA-13] (M = K⁺, Cs⁺) frameworks were prepared by postsynthetic exchange of interchannel dimethylammonium cations. Moreover, it was shown that CO molecules can be selectively bound at Cu(I) sites of [Cu^I₃(pz)₄]⁻ units, whereas Cu(II) paddle-wheel units bind selectively NH₃ molecules.