Molecular Sieving of Propyne/Propylene by a Scalable Nanoporous Crystal with Confined Rotational Shutters

Soft porous coordination polymers (PCPs) have the remarkable ability to recognize similar molecules as a result of their structural dynamics. However, their guest-induced gate-opening behaviors often lead to issues with selectivity and separation efficiency, as co-adsorption is nearly unavoidable. Herein, we report a strategy of a confined-rotational shutter, in which the rotation of pyridyl rings within the confined nanospace of a halogen-bonded coordination framework (NTU-88) creates a maximum aperture of 4.4 angstrom, which is very close to the molecular size of propyne (C3H4: 4.4 angstrom), but smaller than that of propylene (C3H6: 5.4 angstrom). This has been evidenced by crystallographic analyses and modelling calculations. The NTU-88o (open phase of activated NTU-88) demonstrates dedicated C3H4 adsorption, and thereby leads to a sieving separation of C3H4/C3H6 under ambient conditions. The integrated nature of high uptake ratio, considerable capacity, scalable synthesis, and good stability make NTU-88 a promising candidate for the feasible removal of C3H4 from C3H4/C3H6 mixtures. In principle, this strategy holds high potential for extension to soft families, making it a powerful tool for optimizing materials that can tackle challenging separations with no co-adsorption, while retaining the crucial aspect of high capacity. A soft nanoporous crystal has been developed that can separate propyne/propylene mixtures by sieving. This occurs by the rotational movement of pyridyl rings within this framework creating a pore with a maximum size of 4.4 angstrom, thereby facilitating the adsorption of propyne while completely excluding propylene.image

Automated summary

A soft nanoporous crystal has been developed that can separate propyne/propylene mixtures by sieving. This occurs by the rotational movement of pyridyl rings within this framework creating a pore with a maximum size of 4.4 angstrom, thereby facilitating the adsorption of propyne while completely excluding propylene.