Stability vs. reactivity: understanding the adsorption properties of Ni-3(BTP)(2) by experimental and computational methods

FTIR spectroscopy and ab initio molecular modelling have been employed to probe the interaction between CO and Ni-3(BTP)(2), a thermally and chemically stable MOF. A combination of low pressure adsorption isotherms and FTIR spectroscopy has been utilised to study the material for its interaction with CO2 and H-2. The experimental results indicate that despite an abundance of Ni2+ coordination vacancies in the activated sample, the molecular probes considered in this study do not interact with them. These findings are in alignment with the data obtained by molecular modelling, in which it is shown that the unreactive diamagnetic, low spin state is more stable. Due to the strong N-donor character of the pyrazolate ligands on this material, the electrostatic potential map of the optimized low spin structure does not show any evidence of a region of positive potential typical of open metal sites.