Isoreticular Microporous Metal-Organic Frameworks for Carbon Dioxide Capture

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Metal-organic frameworks (MOFs) are promising materials for gas adsorption and separation.
• Tailoring MOF pore structures is crucial for optimizing gas capture efficiency.
• Selective capture of carbon dioxide (CO2) from flue gas (N2) and natural gas (CH4) is an important environmental challenge.

Purpose of the Study:

• To synthesize and characterize novel copper-based MOF analogues using the isoreticular principle.
• To investigate the effect of pore structure modification on CO2 adsorption capacity and selectivity.
• To evaluate the performance of the synthesized MOFs for CO2 separation from N2 and CH4 at ambient conditions.

Main Methods:

• Synthesis of two copper MOF analogues using a 4-substituted isophthalate linker (nitro vs. bromo group).
• Characterization of MOF structures and pore dimensions using X-ray diffraction and gas adsorption analysis.
• Measurement of CO2, N2, and CH4 adsorption isotherms at 1 atm and 298 K.
• Determination of CO2/N2 selectivity using mixture adsorption experiments and dynamic breakthrough tests.

Main Results:

• A new microporous MOF, CuBDC-NO2 (UTSA-93), with a compact pore structure (6.0 × 7.0 Ų) was successfully synthesized.
• The nitro-functionalized MOF exhibited a higher CO2 adsorption capacity (2.40 mmol g⁻¹) compared to the bromo-analogue (1.08 mmol g⁻¹).
• CuBDC-NO2 demonstrated enhanced CO2/N2 selectivity (28) over the bromo-MOF (25), indicating improved separation potential.

Conclusions:

• The isoreticular principle effectively allows for tuning MOF pore environments for selective gas capture.
• The nitro-functionalized MOF (CuBDC-NO2) shows superior performance for CO2 capture and separation applications.
• Dynamic breakthrough experiments confirm the practical utility of CuBDC-NO2 for CO2/N2 mixture separation.