Synthesis of copper–zinc bimetallic imidazolate framework compounds and the structure of Cu(I)-containing Cu2Zn(N2C3H3)4

Copper(II)–zinc(II) bimetallic imidazolate metal–organic framework compounds of composition CuaZnbIm2(a + b) (Im = C3H3N2), including Cu2ZnIm6 (1), were prepared in high yields from the metal oxides under mild aqueous conditions using a novel acid catalysis method. Mild acidic hydrothermal treatment of paramagnetic 1 (≥120 °C) gave diamagnetic Cu(I)-containing Cu2ZnIm4 (2) in high yield. The formation mechanism of 2 involves electron transfer from Im− to Cu(II), with concomitant formation of the unusual cyclotriimidazole, C9H6N6. Air-stable 2, characterized by single-crystal X-ray diffraction, crystallized in the tetragonal space group P4¯21c, with a = b = 10.9623(3), c = 6.3231(4) Å, α = β = γ = 90°, V = 759.86(6) Å3, and Z = 1.

Graphical abstractA convenient acid-catalyzed synthesis of metal imidazolate frameworks from metal oxides provided heterometal-doped zinc imidazolates, including CoxZn(1−x)Im2 (Im = C3H3N2), and Cu(II)–Zn(II) bimetallic imidazolate metal–organic framework (MOF) compounds, CuaZnbIm2(a + b). Mild hydrothermal treatment of Cu2ZnIm6 provided air-stable Cu(I) Cu2ZnIm4 (2), which was structurally characterized.Figure optionsDownload full-size imageDownload as PowerPoint slide