Optimizing Propylene/Propane Sieving Separation through Gate‐Pressure Control within a Flexible Organic Framework

The separation of propylene (C3H6) and propane (C3H8) is of great significance in the chemical industry, which poses a challenge due to their almost identical kinetic diameters and similar physical properties. In this work, we synthesized an ultramicroporous flexible hydrogen‐bonded organic framework (named HOF‐FJU‐106) by using molecule 2,3,6,7‐tetra(4‐cyanophenyl)tetrathiafulvalene (TTF‐4CN). The formation of the dimer causes the TTF‐4CN molecular to bend and weaken π‐stacked interactions, coupled with the flexibility of C≡N···H–C hydrogen bonds, which leads to reversible conversion between open and closed frameworks through the mutual slip of adjacent layers/columns under activation and stimulation of gas molecules. Through gas adsorption isotherms and adsorption enthalpy, HOF‐FJU‐106a exhibited adaptive adsorption and stronger binding affinity for C3H6, and presented a recorded gas uptake ratio of C3H6/C3H8 (23.77) among presentative HOF materials at room temperature to date. Importantly, the flexible HOF‐FJU‐106a shows an interesting phenomenon about the reversible gate pressure control under variable temperature, which realized the gas adsorption and separation performance enhancement for the binary C3H6/C3H8 mixtures. This strategy through designing HOFs with thermoregulatory gating effect is a powerful way to maximize the performance of materials.