Commensurate CO₂ Capture, and Shape Selectivity for HCCH over H₂CCH₂, in Zigzag Channels of a Robust Cu^I(CN)(L) Metal–Organic Framework

A novel copper­(I) metal–organic framework (MOF), {[Cu^I₂(py-pzpypz)₂(μ-CN)₂]·MeCN}_n (1·MeCN), with an unusual topology is shown to be robust, retaining crystallinity during desolvation to give 1, which has also been structurally characterized [py-pzpypz is 4-(4-pyridyl)-2,5-dipyrazylpyridine)]. Zigzag-shaped channels, which in 1·MeCN were occupied by disordered MeCN molecules, run along the c axis of 1, resulting in a significant solvent-accessible void space (9.6% of the unit cell volume). These tight zigzags, bordered by (Cu^ICN)_n chains, make 1 an ideal candidate for investigations into shape-based selectivity. MOF 1 shows a moderate enthalpy of adsorption for binding CO₂ (−32 kJ mol^–1 at moderate loadings), which results in a good selectivity for CO₂ over N₂ of 4.8:1 under real-world operating conditions of a 15:85 CO₂/N₂ mixture at 1 bar. Furthermore, 1 was investigated for shape-based selectivity of small hydrocarbons, revealing preferential uptake of linear acetylene gas over ethylene and methane, partially due to kinetic trapping of the guests with larger kinetic diameters.