Spin-Crossover Modification through Selective CO₂ Sorption

We present a spin-crossover FeII coordination polymer with no permanent channels that selectively sorbs CO2 over N2. The one-dimensional chains display internal voids of ∼9 Å diameter, each being capable to accept one molecule of CO2 at 1 bar and 273 K. X-ray diffraction provides direct structural evidence of the location of the gas molecules and reveals the formation of OCO­(δ–)···π interactions. This physisorption modifies the spin transition, producing a 9 K increase in T1/2.