Bioinspired “Intermolecular Pocket” in Soft Molecular Crystal of Porous Organic Cage Exhibiting Reversible Guest Recognition

Porous Organic Cages (POCs) have gathered a lot of attention in sorts of fields. Previous studies often focused on the functionalization of their intrinsic porosity, while the utilization of the extrinsic porosity has been seldom reported. To date, the rational construction of functionalized extrinsic porosity in POCs is a serious challenge, which still relies on trial and error. Inspired by hydrophobic proteins, in the contribution, a POC (namely NKPOC-DS) is obtained with hydrophobic "intermolecular pocket" as extrinsic porosity constructed through the assembly of disulfide bonds with hydrophobic groups, facilitating strong supramolecular interactions as confirmed by Electrostatic Potential (ESP) maps and single-crystal X-ray diffraction analysis. Notably, NKPOC-DS exhibits a unique C₂H₆-selective "breathing behaviour" due to the presence of softness in its extrinsic porosity, which does not extend to other gases such as C₂H₄, CH₄, CO₂, N₂, and H₂. Such specific recognition of C₂H₆ thus provides NKPOC-DS with the ability to preferentially adsorb C₂H₆ from a C₂H₆/C₂H₄ mixture. The innovative approach of biomimicry in the design of functional POCs provides new insights into manipulating the packing of cages, paving the way for potential applications in guest recognition and adsorption separations.