Tunable Microporous Bimetallic Carboxylate-Pyrazolate Metal-Organic Frameworks for CO₂ Capture

Area of Science:

• Materials Science
• Chemistry
• Chemical Engineering

Background:

• Metal-organic frameworks (MOFs) are promising for carbon capture.
• Designing MOFs with tunable properties is essential for efficient CO2 sorption.
• Hydrophilicity of MOFs can negatively impact CO2 uptake in humid environments.

Purpose of the Study:

• To synthesize and characterize novel heterometallic ultramicroporous MOFs.
• To investigate the effect of metal coordination geometry on MOF properties and CO2 capture performance.
• To design MOFs with reduced water affinity for efficient CO2 capture under humid conditions.

Main Methods:

• Synthesis of heterometallic MOFs (MIP-212(Al/Cu) and MIP-212(Al/Zn)) using a hard-soft acid-base design strategy.
• Structural characterization of the pyrazolate-carboxylate architectures.
• Gas sorption measurements (CO2, N2) under various conditions (pressure, humidity).
• Ideal Adsorbed Solution Theory (IAST) calculations for selectivity.

Main Results:

• Two robust MOFs, MIP-212(Al/Cu) and MIP-212(Al/Zn), with dual tunnel-like pores were synthesized.
• MIP-212(Al/Cu) showed high CO2 uptake and selectivity but was sensitive to humidity due to open metal sites.
• MIP-212(Al/Zn), with suppressed open metal sites, exhibited lower water affinity and superior CO2 breakthrough performance under humidity.

Conclusions:

• Metal coordination geometry in MOFs is a key factor in modulating hydrophilicity and sorption behavior.
• The Zn-based MOF (MIP-212(Al/Zn)) demonstrates potential for efficient CO2 capture in realistic, moist environments.
• This work enables the rational design of advanced MOFs for targeted gas separation applications.