Host-Guest Interaction Modulation in Porous Coordination Polymers for Inverse Selective CO₂ /C₂ H₂ Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Controlling gas sorption in porous materials is crucial for molecular recognition and industrial separations.
• Achieving inverse selectivity, where a high-affinity gas's adsorption is reduced while a low-affinity gas's adsorption is increased, remains a significant challenge.
• Separating carbon dioxide (CO2) from acetylene (C2H2) is vital for acetylene purification.

Purpose of the Study:

• To demonstrate an "opposite action" strategy for enhancing CO2/C2H2 selectivity in porous coordination polymers (PCPs).
• To synthesize novel ultramicroporous PCP physisorbents with improved gas adsorption properties.
• To achieve efficient separation of C2H2 from CO2/C2H2 mixtures.

Main Methods:

• Precise steric design of channel pores in PCPs using an amino group as an additional interacting site.
• Synthesis of two new isostructural ultramicroporous PCP physisorbents.
• Gas sorption measurements at 298 K and density functional theory (DFT) calculations to verify selectivity origins.

Main Results:

• The modified PCPs exhibited synergetic increases in CO2 adsorption and suppression of C2H2 adsorption.
• The synthesized physisorbents demonstrated the highest CO2 uptake and CO2/C2H2 volume uptake ratio at 298 K.
• DFT calculations confirmed the origin of the observed specific selectivity.

Conclusions:

• The "opposite action" strategy effectively controls gas sorption and enhances CO2/C2H2 selectivity.
• The novel ultramicroporous PCPs show excellent performance for C2H2 purification from CO2/C2H2 mixtures.
• The materials exhibit remarkable stability and recyclability, making them suitable for industrial applications.