Benchmark Acetylene Binding Affinity and Separation through Induced Fit in a Flexible Hybrid Ultramicroporous Material

Structural changes at the active site of an enzyme induced by binding to a substrate molecule can result in enhanced activity in biological systems. Herein, we report that the new hybrid ultramicroporous material sql‐SIFSIX‐bpe‐Zn exhibits an induced fit binding mechanism when exposed to acetylene, C 2 H 2 . The resulting phase change affords exceptionally strong C 2 H 2 binding that in turn enables highly selective C 2 H 2 /C 2 H 4 and C 2 H 2 /CO 2 separation demonstrated by dynamic breakthrough experiments. sql‐SIFSIX‐bpe‐Zn was observed to exhibit at least four phases: as‐synthesised (α); activated (β); and C 2 H 2 induced phases (β′ and γ). sql‐SIFSIX‐bpe‐Zn‐β exhibited strong affinity for C 2 H 2 at ambient conditions as demonstrated by benchmark isosteric heat of adsorption ( Q st ) of 67.5 kJ mol −1 validated through in situ pressure gradient differential scanning calorimetry (PG‐DSC). Further, in situ characterisation and DFT calculations provide insight into the mechanism of the C 2 H 2 induced fit transformation, binding positions and the nature of host‐guest and guest‐guest interactions.