Single-atom ligand changes affect breathing in an extended metal-organic framework

Area of Science:

• Materials Science
• Chemistry
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) are synthesized using organic linkers and metal ions.
• 4,4′-biphenyldicarboxylic acid (bpdc) is a common organic linker for MOF synthesis.
• Isoreticular MOFs are frameworks with the same topology but different linker/metal composition.

Purpose of the Study:

• To synthesize and characterize MOFs using 2-phenylpyridine-5,4′-dicarboxylic acid (dcppy) as an organic linker.
• To compare the structural and gas sorption properties of dcppy-based MOFs with isostructural bpdc-based MOFs.
• To investigate the effect of the pyridine group in dcppy on MOF properties, particularly framework flexibility and gas uptake.

Main Methods:

• Solvothermal synthesis of MOFs using dcppy and bpdc linkers with Zr, Al, and Zn metal ions.
• Characterization using powder X-ray diffraction (PXRD), single X-ray diffraction (XRD), and thermogravimetric analysis (TGA).
• Gas sorption analysis (N2 and CO2) to evaluate adsorption properties and framework behavior.

Main Results:

• Successfully synthesized isoreticular MOFs including UiO-67-dcppy, DUT-5-dcppy, DMOF-1-dcppy, and BMOF-1-dcppy.
• Frameworks from dcppy and bpdc generally showed similar structures and thermal stability.
• BMOF-1-dcppy exhibited significant N2 and CO2 hysteresis, indicating framework flexibility, unlike the low uptake in BMOF-1-bpdc.

Conclusions:

• The pyridine moiety in dcppy influences interpenetrated MOF structures, leading to weakened π-π interactions and enhanced framework flexibility.
• This flexibility in BMOF-1-dcppy results in distinct gas sorption behavior compared to its bpdc analogue.
• Dcppy is a viable linker for creating MOFs with tunable properties, particularly for applications requiring framework dynamics.