LOOKING INTO POROUS MATERIALS WITH SOLID STATE NMR AND RELAXOMETRY

Solid porous materials find widespread domestic and industrial applications, including construction and building, gas separation and storage, filtration and purification, ion exchange, energy storage, and heterogeneous catalysis. This class of materials encompasses fully inorganic or organic systems and organic/inorganic hybrid systems, with both crystalline and amorphous structure. The macroscopic behaviour of porous materials is strongly related to the structural and dynamic properties of their building units at molecular level, as well as to the interactions of the porous matrix with guest molecules. Solid-state NMR (SSNMR) spectroscopy and NMR relaxometry represent very powerful techniques for characterizing microscopic properties over wide space and time scales and drawing structure-properties relationships in porous materials. Thanks to the possibility of exploiting many different NMR-active nuclei and a variety of nuclear observables, the application of NMR methods allows molecular and supramolecular structure and motions of specific moieties of the porous materials to be investigated. In addition, information can be acquired on the dynamics of gaseous or liquid guests hosted in the porous matrix, as well as on host-guest interactions. In this lecture, the applicability of SSNMR spectroscopy and relaxometry experiments for looking inside porous materials will be discussed presenting several examples taken from the recent research work of the Pisa SSNMR group. In particular, the lecture will focus on structural properties and hydration of innovative cements characterized by multinuclear SSNMR [1,2] and 1H relaxometry [3,4] and on structural and dynamic properties and host-guest interactions of metal organic frameworks (MOFs) [5] and polymers of intrinsic microporosity (PIMs) for CO2 capture investigated by multinuclear SSNMR. Acknowledgements PRIN MUR (DOMINO project n. 2020P9KBKZ) is acknowledged for partially financing the research. References [1] M. Tonelli, F. Martini, L. Calucci, E. Fratini, M. Geppi, F. Ridi, S. Borsacchi, P. Baglioni, Dalton Trans., 2016, 45, 3294. [2] F. Martini, M. Tonelli, E. Fratini, M. Geppi, F. Ridi, S. Borsacchi, L. Calucci, Cem. Concr. Res., 2017, 102, 60-67. [3] F. Martini, S. Borsacchi, M. Geppi, M. Tonelli, F. Ridi, L. Calucci, Micropor. Mesopor. Mater., 2018, 269, 26-30. [4] F. Martini, S. Borsacchi, M. Geppi, C. Forte, L. Calucci, J. Phys. Chem. C 2017, 121, 26851-26859. [5] M. Cavallo, C. Atzori, M. Signorile, F. Costantino, D. Morelli Venturi, A. Koutsianos, K.A. Lomachenko, L. Calucci, F. Martini, A. Giovanelli, M. Geppi, V. Crocellà, M. Taddei, J. Mater. Chem. A, 2023, 11, 5568.