Linear Anion Chain-Assembled Nonporous Swelling Molecular Sieve for Benchmark C2–C4 Hydrocarbon Separations

Abstract

Designing ideal materials with simultaneously high selectivity, high capacity, fast kinetics, and moderate regeneration for hydrocarbon separations remains challenging, restricting the advance of nonthermal-driven gas separation technologies. Herein, we reported a nonporous ClO₄^– -functionalized swelling molecular sieve CuClO₄bipy·H₂O that is assembled with 1D metal–organic linear chains via water-mediated hydrogen bonding. Destroying the hydrogen-bond network that connects linear chains enables the transformation from nonporous to adaptive porous structures upon gas exposure via chain shift, as indicated by Rietveld refinement of the structure of gas-loaded CuClO₄bipy. The easily and rapidly reversible swelling nature of CuClO₄bipy enables its fast kinetics and easy regeneration under ambient conditions. Meanwhile, in situ DRIFTS and ex situ Raman experiments reveal that the coordinated ClO₄^– anions and Cu open metal sites within CuClO₄bipy endow the swelling structure with specific recognition ability toward molecules (e.g., acetylene, propyne, and butadiene) while excluding other molecules (e.g., alkanes, alkenes, and carbon dioxide), establishing CuClO₄bipy as a new benchmark material for C2–C4 hydrocarbon separation. The work unveils the strategy of swelling molecular sieves with optimal thermodynamic and kinetic behaviors for challenging gas separations.