Hydrogen thermal desorption spectra: insights from molecular simulation

Thermal desorption spectra of a number of metal-organic frameworks were studied using grand canonical Monte Carlo simulation. Our simulation results are in qualitative agreement with experimental results but also show that great care must be taken when choosing the force field to describe the hydrogen/framework interaction. As the simulations additionally yield the positions and potential energies of the adsorbed molecules it is straightforward to assign the peaks and features in the thermal desorption spectra to specific adsorption sites. We show that the location of the peaks is directly related to the hydrogen-framework interaction which is a complex function of the chemical and topological environment of the pore space, the pore size and the presence of specific interaction sites such as open metal sites. Finally, we demonstrate that an IRMOF-8 sample used to obtain an experimental thermal desorption spectrum must have indeed been catenated as previously suspected. Overall, molecular simulation is a useful tool to complement the interpretation of experimental thermal desorption spectra.