Direct Crystallographic Observation of CO2 Captured in Zig Zag Channels of a Copper(I) Metal-Organic Framework.

Single crystal X-ray diffraction has been used to study the CO2 absorption sites in a microporous Cu-MOF, [CuI2(py-pzpypz)2(μ-CN)2]n (1) (where py-pzpypz = 4-(4-pyridyl)-2,5-dipyrazyl-pyridine), which features zigzag-shaped channels, at a range of CO2 pressures (1, 5, and 10 bar) and at two temperatures (240 and 298 K). Unlike the acetonitrile molecules in the as-synthesized MOF, 1·MeCN, the CO2 molecules in 1·nCO2 (n = 0.8, 0.7, 0.45) are preferentially centered on the vertices of each zig and zag, which allows for weak (azine) C-H···OCO interactions with the H atoms on the electron-deficient pyrazine and pyridine rings of the MOF.