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

Abstract

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.