Selective CO₂ uptake mimics dissolution in highly fluorinated non-porous crystalline materials

Area of Science:

• Materials Science
• Chemistry
• Chemical Engineering

Background:

• Efficient separation of carbon dioxide (CO2) is crucial for methane (CH4) gas purification and blue hydrogen production.
• Existing methods for CO2 separation often face challenges in selectivity and efficiency.

Purpose of the Study:

• To develop novel materials for selective CO2 capture from gas mixtures.
• To investigate the mechanism of CO2 uptake in flexible silver coordination polymers (AgCPs).

Main Methods:

• Synthesis and characterization of flexible silver coordination polymers (AgCPs) with varying perfluoroalkyl chain lengths.
• Gas sorption analysis to evaluate CO2 and CH4 uptake capacities and selectivities.
• In situ single-crystal and powder X-ray diffraction to visualize CO2 binding and structural changes.

Main Results:

• AgCPs demonstrate selective CO2 uptake above a gate pressure, functioning via a dissolution-like mechanism.
• CO2 sorption properties are tunable by altering the perfluoroalkyl chain length of ligands.
• AgCPs exhibit negligible CH4 uptake due to alkane-perfluoroalkane immiscibility, confirming selectivity.

Conclusions:

• Flexible AgCPs with latent porosity offer a promising platform for selective CO2 capture.
• The observed CO2 selectivity over CH4 is attributed to a unique dissolution mechanism facilitated by fluorinated, mobile regions within the AgCPs.
• In situ X-ray diffraction confirmed the gating mechanism and structural dynamics governing CO2 uptake.