Pore surface fluorination and PDMS deposition within commercially viable metal-organic framework for efficient C₂H₂/CO₂ separation

Removing CO₂ impurities from C₂H₂/CO₂ mixtures is an essential process for producing high-purity C₂H₂ under high humidity. High-stability and low-cost metal-organic frameworks (MOFs) have great potential in C₂H₂/CO₂ industrial separation. However, due to the complementary adsorption of H₂O and CO₂, water vapor has a negative impact on the implementation of C₂H₂ purification. Herein, we propose a synergistic strategy of pore surface functionalization and polydimethylsiloxane (PDMS) deposition to avoid the influence of water vapor while improving C₂H₂/CO₂ separation performance. A commercially available metal-organic framework (ALP-MOF-1) was used as a template to functionalize its pore surface with CH₃, Br, and F. The optimized material ALP-MOF-1(F) exhibits the highest C₂H₂ uptake (117.78 cm³/g at 298 K and 10⁶ Pa) and C₂H₂/CO₂ uptake ratio (3.1) among ALP-MOF systems. Computational simulations show that the well-matched pore space and the significant electronegativity and polarizability of the fluorine groups on the pore surface jointly enhance the framework-C₂H₂ interaction. Furthermore, the deposition of PDMS on ALP-MOF-1 and ALP-MOF-1(F) significantly improves their C₂H₂/CO₂ separation stability under 80% humidity conditions.