Highly selective C₂H₄/C₂H₂ separation using a cyano-functionalized alkadiyne-pyrene conjugated framework membrane.

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Separating gases like ethylene and acetylene is crucial but challenging due to similar sizes.
• Existing methods often lack efficiency and selectivity.

Purpose of the Study:

• To design and fabricate a highly selective membrane for ethylene/acetylene separation.
• To investigate the role of cyano groups in enhancing separation performance.

Main Methods:

• Incorporation of cyano (CN) groups into a poly(1,3,6,8-tetraethynylpyrene) (PTEP) conjugated framework membrane.
• Density Functional Theory (DFT) and Molecular Dynamics (MD) simulations.
• Experimental measurement of gas permeance and selectivity.

Main Results:

• The CN-functionalized membrane exhibited significantly narrowed pores and selective C-H⋯N hydrogen bonding with ethylene.
• DFT calculations showed a much lower diffusion barrier for ethylene (0.87 kcal mol⁻¹) than acetylene (6.87 kcal mol⁻¹).
• MD simulations revealed a dynamic selectivity of 46.7 ± 4.1 for C₂H₄/C₂H₂ separation, with high permeance values.

Conclusions:

• The developed membrane offers a versatile strategy for precise control of pore size and chemical functionality.
• This approach enables advanced gas separation performance, surpassing many existing covalent organic framework (COF) membranes.
• Provides valuable insights for designing next-generation separation membranes.