A Chemically Cross-Linked NbO-Type Metal-Organic Framework: Cage or Window Partition?

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) are porous materials with tunable structures.
• Chemical cross-linking offers a method to enhance MOF stability and modify properties.
• Understanding the impact of cross-linking on MOF topology and adsorption is crucial for targeted applications.

Purpose of the Study:

• To synthesize a chemically cross-linked MOF, ZJNU-80, based on the NbO-type NOTT-101 structure.
• To investigate the structural consequences of chemical cross-linking on the MOF's topology and pore characteristics.
• To evaluate the effect of chemical cross-linking on the gas adsorption properties of the MOF for various gases.

Main Methods:

• Preparation of ZJNU-80 using a presynthetically cross-linked octacarboxylate ligand.
• Single-crystal X-ray structure analysis to determine the MOF's topology and the role of cross-linking groups.
• Gas adsorption studies at ambient temperature using CO2, CH4, N2, and 1-butene.

Main Results:

• ZJNU-80 adopts the same topology as NOTT-101, with cross-linking groups partitioning the windows, not the cages.
• Despite reduced porosity, ZJNU-80 exhibits similar low-pressure adsorption to NOTT-101 for CO2, CH4, and N2.
• Adsorption of 1-butene, a larger molecule, is significantly affected by the altered window structure at near-saturation conditions.

Conclusions:

• Chemical cross-linking of MOFs can preserve pore size distribution for small gas molecules.
• Window partitioning due to cross-linking influences the packing and adsorption of larger molecules.
• This study provides fundamental insights into structure-property relationships in chemically modified MOFs for gas adsorption.