An Amine-Functionalized Ultramicroporous Metal-Organic Framework for Postcombustion CO₂ Capture

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Global warming is accelerated by CO2 emissions from flue gas.
• Energy-efficient physisorption using metal-organic frameworks (MOFs) is a promising CO2 capture method.
• Designing MOFs with enhanced CO2 affinity and stability is crucial.

Purpose of the Study:

• To present a novel cuprous-based ultramicroporous MOF, Cu(adci)-2, for enhanced CO2 capture.
• To investigate the structural and adsorption properties of Cu(adci)-2.
• To evaluate the CO2 capture performance of Cu(adci)-2 under varying humidity conditions.

Main Methods:

• Rational synthesis of Cu(adci)-2 by combining aromatic amine functionalization and ultramicroporosity.
• Synchrotron powder X-ray diffraction and Rietveld analysis for structural determination.
• CO2 adsorption capacity and isosteric heat measurements.
• Breakthrough experiments under dry and humid conditions.
• Monte Carlo simulations and radial distribution analysis for binding site prediction.

Main Results:

• Cu(adci)-2 exhibits a high CO2 adsorption capacity (2.01 mmol g-1 at 298 K and 15 kPa) and low isosteric heat of adsorption (27.5 kJ mol-1).
• The material features one-dimensional square-shaped channels with oriented NH2 groups.
• CO2 capture ability is retained under 60% relative humidity.
• Preferential CO2 binding sites are located between ligands, forming a sandwich-like structure.

Conclusions:

• Cu(adci)-2 is a promising MOF for energy-efficient CO2 capture from flue gas.
• Aromatic amine functionalization and ultramicroporosity contribute to enhanced CO2 adsorption.
• The material's stability in humid conditions makes it suitable for real-world applications.