Ni₈ Carboxylate Metal-Organic Frameworks

Area of Science:

• Materials Science
• Inorganic Chemistry
• Nanotechnology

Background:

• Octanuclear nickel cubes (Ni8) are valuable building blocks for metal-organic frameworks (MOFs) due to their symmetry and stability.
• Conventional Ni8-based MOFs typically utilize pyrazolate ligands.
• There is a need for Ni8 MOFs constructed with alternative ligands for diverse applications.

Purpose of the Study:

• To synthesize novel Ni8-based MOFs using exclusively carboxylic acid ligands.
• To investigate the structural properties and stability of these new materials.
• To evaluate their performance in acetylene/carbon dioxide (C2H2/CO2) separation.

Main Methods:

• Solvothermal synthesis of Ni8-based metal-organic frameworks (MOFs).
• Characterization of synthesized materials (e.g., structural analysis, stability testing).
• Gas adsorption and separation experiments, including C2H2/CO2 mixture analysis under varying humidity.

Main Results:

• Successful synthesis of two carboxylate-based Ni8 MOFs (NNM-2 and NNM-3) with fcu topology.
• Both NNM-2 and NNM-3 exhibit stability across a wide pH range.
• NNM-2 demonstrated significant C2H2/CO2 separation (36.4 min g-1 retention time difference) and maintained performance at ~100% relative humidity due to its hydrophobic pores.

Conclusions:

• Carboxylic acid ligands can effectively replace pyrazolate ligands in constructing Ni8-based MOFs.
• The synthesized carboxylate-based Ni8 MOFs (NNM-2 and NNM-3) offer robust structural integrity and chemical stability.
• NNM-2 shows promising potential for selective C2H2/CO2 separation, particularly in humid environments, highlighting its practical applicability.