A complete spectroscopic and adsorptive study of a thermally robust pyrazolato-based PCP containing cubic octanuclear Ni(II) clusters

The pyrazolato-based porous coordination polymer (PCP) [Ni8(μ4-OH)4(μ4-OH2)2(μ4-PBP)6] (NiPBP, H2PBP = 4,4’-bis(1H-pyrazol-4-yl)biphenyl) is built upon octametallic hydroxo clusters reciprocally connected by organic spacers. This material is a very promising candidate for gas adsorption applications, owing to its remarkable thermal stability (up to 400 °C in air) and its high void volume (70%) [1]. NiPBP was selected as a proof-of-concept material to demonstrate how an optimized set of laboratory and synchrotron techniques can concur to create a comprehensive and coherent picture, relating (average and local) structural features to adsorptive properties. To this aim, the response of NiPBP toward different gases, retrieved by gas adsorption measurements (N2 at 77 K, in the low pressure region; H2 at 77 K, in the high pressure region), was explained in terms of local-level details. In particular the electronic structure of the material was deeply investigated combining laboratory UV-Vis spectroscopy, X-ray absorption near edge structure (XANES) and resonant inelastic X-ray scattering (RIXS) [2].