High-resolution inelastic neutron scattering and neutron powder diffraction study of the adsorption of dihydrogen by the Cu(II) metal-organic framework material HKUST-1

- Binding sites for dihydrogen in a metal-organic framework have been identified.
- The combination of diffraction and spectroscopy shows competitive filling of various adsorption sites.
- Inelastic neutron scattering over wide-momentum transfer reveals new models for hydrogen-framework interactions.

We present new high-resolution inelastic neutron scattering (INS) spectra (measured using the TOSCA and MARI instruments at ISIS) and powder neutron diffraction data (measured on the diffractometer WISH at ISIS) from the interaction of the prototypical metal-organic framework HKUST-1 with various dosages of dihydrogen gas. The INS spectra show direct evidence for the sequential occupation of various distinct sites for dihydrogen in the metal-organic framework, whose population is adjusted during increasing loading of the guest. The superior resolution of TOSCA reveals subtle features in the spectra, not previously reported, including evidence for split signals, while complementary spectra recorded on MARI present full information in energy and momentum transfer. The analysis of the powder neutron patterns using the Rietveld method shows a consistent picture, allowing the crystallographic indenisation of binding sites for dihydrogen, thus building a comprehensive picture of the interaction of the guest with the nanoporous host.