CO 2 -actuated spin transition tuning in an interdigitated Hofmann-type coordination polymer.

The increased anthropogenic emission level of CO 2 urges the development of CO 2 -responsive materials, but is it possible to regulate the inherent electronic properties through weak physisorption of a ubiquitous gas such as CO 2 ? Herein, we intended to answer this imperative question by the first case of CO 2 -actuated variable spin-state stabilisation in an interdigitated Hofmann-type coordination polymer [Fe II Pd(CN) 4 L 2 ] (1, L = methyl isonicotinate), showing a wide shift in transition temperature ( T eq ) from 178 K at P CO 2 = 0 kPa to 229 K at P CO 2 = 100 kPa. Interestingly, the emergence of a stepped behaviour in the heating process below P CO 2 = 10 kPa and overlapping magnetic susceptibility values above P CO 2 = 10 kPa elucidate the selective LS state stabilisation solely correlated with the extent of CO 2 accommodation. Based on the magnetic response and phase transition diagrams obtained under respective P CO 2 , a plausible scenario of the spin-state switching can be interpreted as (1 ls + ) → (1 hs + ) → 1 hs at P CO 2 ≤ 10 kPa, → 1 hs at 100 kPa < P CO 2 ≥ 32 kPa and → → 1 hs at 100 kPa, where 1 and 1' represent CO 2 -free and CO 2 -encapsulated states, respectively. The cooperative CO 2 sorption with SCO based on the varied CO 2 pressure corroborates a novel case for developing CO 2 -responsive magnetic materials henceforth.