MOF Metal-organic framework materials show promise for fuel cells

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A team from Northwestern University in the United States has developed and synthesized new metal-organic framework (MOF) materials with ultra-high porosity for the storage of hydrogen or methane.

The research team designed these MOFs fuel-cell powered vehicles. According to the team, the materials are able to store significantly more hydrogen and methane than conventional absorbent materials at safer pressures and at lower costs.

“We’ve developed a better onboard storage method for hydrogen and methane gas for next-generation clean energy vehicles,” said Omar K. Farha, who led the research. “To do this, we used chemical principles to design porous materials with precise atomic arrangement, thereby achieving ultrahigh porosity.”

The highly porous MOFs are based on metal trinuclear clusters. In contrast to other highly porous MOFs, the Northwestern team’s material, NU-1501, exhibits a high gravimetric Brunauer-Emmett-Teller (BET) area of 7310 m2 g−1 and a volumetric BET area of 2060 m2 cm−3 while satisfying the four BET consistency criteria. In simpler terms, a one-gram sample of the team’s material has a surface area that would cover 1.3 American football fields—this is thanks to its nanoscopic pores. NU-1501 MOFs are built from organic molecules and metal ions or clusters. These self-assemble to create multidimensional, highly crystalline, highly porous frameworks.

The team’s new material could be what the gas storage industry has been looking for because many industries and applications require the use of compressed gases. One potential application is that of hydrogen- and methane-powered vehicles that currently require high-pressure compression to operate with the pressure of a hydrogen tank 300 times greater than the pressure in car tyres. However, this pressure is expensive to accomplish due to hydrogen’s low density.

So, developing new materials that are adsorbents—porous solids which bind liquid or gaseous molecules to their surface—and can store gases onboard vehicles at lower pressures could help develop the next generation of fuel cells in carbon-neutral cars and other vehicles. “We can store tremendous amounts of hydrogen and methane within the pores of the MOFs and deliver them to the engine of the vehicle at lower pressures than needed for current fuel cell vehicles,” said Omar K. Farha, who led the research.

The team’s research study was published in Science in April. The team collaborated with scientists at the National Institute for Standards and Technology (NIST) to carry out high-pressure gas sorption experiments.

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