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.