Discrete {Ni40} Coordination Cage: A Calixarene-Based Johnson-Type (J17) Hexadecahedron

Area of Science:

• Materials Chemistry
• Supramolecular Chemistry
• Coordination Chemistry

Background:

• Metal-organic frameworks (MOFs) and coordination cages are extensively studied for gas storage and separation.
• Designing complex polyhedral structures with specific functionalities remains a challenge.

Purpose of the Study:

• To synthesize and characterize a novel Johnson solid-like coordination cage.
• To investigate the gas sorption properties of the synthesized cage, particularly for C3H8 and CH4 separation.

Main Methods:

• The coordination cage was constructed using Ni4-p-tert-butylthiacalix[4]arene (Ni4-TC4A) units as vertices and 5-(pyridin-4-yl)isophthalate (PIP) ligands as linkers.
• The crystal structure was determined, revealing a J17 Johnson solid geometry (gyroelongated square bipyramid).
• Gas sorption isotherms for C3H8 and CH4 were measured to evaluate adsorption capacities.

Main Results:

• A novel hexadecahedronal coordination cage with a J17 Johnson solid geometry was successfully synthesized.
• The cage demonstrated significantly higher adsorption capacity for propane (C3H8) compared to methane (CH4).
• A contrasting 1D polymer structure was observed when using Cobalt (Co4-TC4A) instead of Nickel (Ni4-TC4A) units.

Conclusions:

• The synthesized Ni4-TC4A-based coordination cage is a promising material for selective C3H8/CH4 separation.
• The study highlights the potential of constructing complex polyhedral architectures for targeted gas separation applications.
• The findings underscore the influence of metal centers on the resulting framework topology and properties.