Nanoporous Frameworks with High Porosity and Unexpected Rigid Framework Topologies Based on Odd-Numbered...

Area of Science:

• Materials Science
• Chemistry
• Crystallography

Background:

• Metal-organic frameworks (MOFs) are porous crystalline materials constructed from metal ions and organic linkers.
• The design of novel organic linkers is crucial for creating MOFs with tailored structures and properties.
• Seven-membered rings in linkers can introduce unique geometric constraints, influencing framework topology.

Purpose of the Study:

• To synthesize and characterize new MOFs using novel tetracarboxylic linkers containing seven-membered rings.
• To investigate the structural diversity and porosity of the resulting MOFs, DUT-184 and DUT-193.
• To explore the gas adsorption properties and underlying mechanisms in these new materials.

Main Methods:

• Synthesis of two novel tetracarboxylic linkers featuring seven-membered rings.
• Construction of metal-organic frameworks (MOFs) using these linkers with zinc ions.
• Single-crystal X-ray diffraction for structural determination of DUT-184 and DUT-193.
• Gas adsorption measurements (N₂, Ar, CH₄, CO₂) at low temperatures.
• Grand canonical Monte Carlo (GCMC) simulations for theoretical analysis of adsorption.

Main Results:

• Successful synthesis of two new MOFs, DUT-184 and DUT-193, incorporating dihydro-azepine-containing linkers.
• DUT-184 exhibits a 3D structure formed by interpenetrated 2D nets.
• DUT-193 presents a cubic structure with a previously unreported topology and high mesoporosity.
• DUT-193 demonstrated significant adsorption of N₂, Ar, CH₄, and CO₂.
• GCMC simulations validated experimental adsorption data and elucidated low-pressure adsorption mechanisms.

Conclusions:

• Novel tetracarboxylic linkers with seven-membered rings enable the construction of exotic MOF architectures.
• The unique linker geometry leads to complex and potentially new framework topologies.
• DUT-193 shows promise as a porous material for gas storage and separation due to its high porosity and adsorption capabilities.
• Computational simulations provide valuable insights into the gas adsorption behavior of MOFs at a molecular level.