Direct Observation of Hydrogen Adsorption Sites and Nano-Cage Formation in Metal-Organic Frameworks (MOF)

TL;DR

This study combines neutron diffraction and first-principles calculations to identify hydrogen adsorption sites in MOF5, revealing nano-cluster formation that enhances hydrogen storage potential and opens avenues for designing hydrogen nano-cages.

Contribution

It provides the first detailed identification of hydrogen adsorption sites in MOF5 and demonstrates nano-cage formation, advancing understanding of hydrogen storage mechanisms in MOFs.

Findings

Metal-oxide clusters are primary adsorption sites.

H2 molecules form high-symmetry nano-clusters at low temperature.

H2 uptake reaches as high as 10 wt%.

Abstract

The hydrogen adsorption sites in MOF5 were determined using neutron powder diffraction along with first-principles calculations. The metal-oxide cluster is primarily responsible for the adsorption while the organic linker plays only a secondary role. Equally important, at low temperatures and high-concentration, H2 molecules form unique interlinked high-symmetry nano-clusters with intermolecular distances as small as 3.0 Ang. and H2-uptake as high as 10-wt%. These results hold the key to optimizing MOF materials for hydrogen storage applications and also suggest that MOFs can be used as templates to create artificial interlinked hydrogen nano-cages with novel properties.