Systemic regulation of binding sites in porous coordination polymers for ethylene purification from ternary C2 hydrocarbons

Abstract

The global demand for poly-grade ethylene (C₂H₄) is increasing annually. However, the energy-saving purification of this gas remains a major challenge due to the similarity in molecular properties among the ternary C2 hydrocarbons. To address this challenge, we report an approach of systematic tuning of the pore environment with organic sites (from –COOH to –CF₃, then to –CH₃) in porous coordination polymers (PCPs), of which NTU-73-CH₃ shows remarkable capability for the direct production of poly-grade C₂H₄ from ternary C2 hydrocarbons under ambient conditions. In comparison, the precursor structure of NTU-73-COOH is unable to purify C₂H₄, while NTU-73-CF₃ shows minimal ability to harvest C₂H₄. This is because the changed binding sites in the NTU-73-series not only eliminate the channel obstruction caused by the formation of gas clusters, but also enhance the interaction with acetylene (C₂H₂) and ethane (C₂H₆), as validated by in situ crystallographic and Raman analysis. Our findings, in particular the systematic tuning of the pore environment and the efficient C₂H₄ purification by NTU-73-CH₃, provide a blueprint for the creation of advanced porous families that can handle desired tasks.