Property-Tuned, Defective, and Amorphous MOF Adsorbents via Ligand Tethering

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) are porous materials with tunable properties.
• Oligomerization of ligands before MOF synthesis can influence framework formation.
• Controlling MOF structure and properties is crucial for advanced applications.

Purpose of the Study:

• To investigate the effect of alkyl-tethered ligand dimer length on the synthesis and properties of Cu-DMOF-1 based oligoMOFs.
• To establish a systematic approach for tailoring MOF characteristics through ligand design.
• To evaluate the CO2 adsorption performance of the synthesized oligoMOFs.

Main Methods:

• Synthesis of oligoMOFs using alkyl-tethered ligand dimers (propyl to heptyl).
• Characterization using microcrystal electron diffraction (uED), powder X-ray diffraction (PXRD), imaging, spectroscopy, and thermal analysis.
• Periodic DFT calculations to understand structure-property relationships.
• CO2 adsorption studies to assess performance.

Main Results:

• Tether length systematically influenced MOF crystallinity, crystal size, thermal stability, and porosity.
• Shorter tethers led to defective or amorphous MOFs due to geometric constraints.
• Amorphous propyl(bdc)2-Cu-DMOF-1 showed high BET surface area (941 m2g-1) and enhanced CO2 adsorption (Qst = 26.8 kJ mol-1, selectivity 102).

Conclusions:

• Ligand tether length is a key parameter for controlling MOF self-assembly and properties.
• Systematic variations in MOF structure and defectivity can be achieved solely through tether sizing.
• Tailored oligoMOFs, particularly amorphous ones, demonstrate significant potential for enhanced CO2 capture applications.