Hydrogen storage in microporous metal-organic frameworks.

Area of Science:

• Materials Science
• Chemistry
• Physics

Background:

• Metal-organic frameworks (MOFs) are advanced porous materials with tunable structures.
• Hydrogen storage is a critical challenge for clean energy technologies.

Purpose of the Study:

• To investigate hydrogen adsorption in Metal-organic framework-5 (MOF-5).
• To identify hydrogen binding sites within MOF-5 using inelastic neutron scattering.
• To compare hydrogen uptake in MOF-5 with related isoreticular MOFs (IRMOFs).

Main Methods:

• Synthesis and characterization of MOF-5.
• Gravimetric analysis of hydrogen adsorption at various temperatures and pressures.
• Inelastic neutron scattering (INS) spectroscopy to probe adsorbed hydrogen dynamics.

Main Results:

• MOF-5 demonstrated high hydrogen uptake (4.5 wt% at 78 K) and significant uptake at room temperature (1.0 wt% at 20 bar).
• INS revealed two distinct hydrogen binding sites within MOF-5, attributed to interactions with zinc and the 1,4-benzenedicarboxylate (BDC) linker.
• Isoreticular MOF-6 and MOF-8 exhibited approximately double and quadruple the hydrogen uptake of MOF-5 at room temperature and 10 bar, respectively.

Conclusions:

• MOF-5 exhibits promising hydrogen storage capabilities due to its porous structure and specific binding sites.
• The identified binding sites provide insights into the mechanism of hydrogen adsorption in MOFs.
• Modifying linker groups in isoreticular MOFs can significantly enhance hydrogen storage performance.