KN04 - Metal-Organic Frameworks as Chemical Reactors: X-ray Crystallographic Snapshots of the Confined State

D. Armentano (Università della Calabria, Italy)
E. Pardob (Universitat de València, Spain)
A. Leyva–Pérez (Instituto de Tecnología Química , Spain)

Ultrasmall metal nanoclusters (NCs), consisting of aggregations of less than 10 atoms with a high percentage of them exposed to the external environment, have emerged as formidable catalysts capable to surpass the state-of-the-art catalysts in organic reactions of industrial interest, being thus capable to make feasible certain reactions which are currently financially prohibitive.[1] Such small NCs, that may give rise to a technological leap in a similar way as the irruption of metal nanoparticles (NPs) did, still show important weaknesses regarding the synthetic control of their shape and nuclearity as well as their lack of stability.[2] Metal-Organic Frameworks (MOFs) [3] show unique features to act as chemical nanoreactors for the in-situ synthesis and stabilization of otherwise not accessible functional species and to use single crystal X-ray crystallography as a definitive characterization tool, which offers the unique possibility –among porous materials– to contrast the success of synthetic methodologies, and even more important, to follow/understand what is actually happening within MOFs channels. Supporting these clusters within MOFs is a very promising strategy. MOFs own regular and well-defined channels and exhibit a fascinating host-guest chemistry. [3] In principle, they are suitable platforms to synthesize, in a controlled manner, metal clusters below the nanometer allowing to gain information about their nature by means of X–ray crystallography, to shed light on every single step during their synthetic route.[4] Even Supramolecular Coordination Compounds (SCCs) with targeted properties can be self-assembled and stabilized within a MOF.
Here we report on the MOF-mediated chemical synthesis of structurally and electronically well–defined ultrasmall Pt2, Pt1+1, FeIII, RuIII and [Pd4]2+ catalysts, together with PdII SCCs built within the confined space of preformed MOFs (SCCs@MOF) and their post-assembly metalation to give a PdII-AuIII supramolecular assembly, all crystallographically underpinned.[5] These results open new avenues in both the synthesis of novel NCs and SCCs and their use on heterogeneous metal-based Supramolecular Catalysis. Reactions in which the resulting hybrid materials outperform state–of–the–art metal catalysts will be illustrated.

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[2] Lei Y. et al., Science 2010, 328, 224–228.
[3] O’Keeffe, M.; Yaghi O. M. et al., Science 2013, 341, 974. (b) Férey, G. et al., Chem. Soc. Rev. 2017, 46, 3104–3107; (c) Zhou, H.-C. et al., Adv. Mater. 2018, 1704303.
[4] (a) Corma, A.; Leyva-Perez, A; . Armentano, D.; Pardo E. et al., Nat. Mater. 2017, 16, 760; (b) A. Leyva-Perez, D. Armentano, E. Pardo et al., J. Am. Chem. Soc. 2016, 138, 7864–7867.; (c) D. Armentano, E. Pardo et al., Angew. Chem., Int. Ed. 2016, 55, 11167–11172; (d) Farha, O. K. et al., Science 2017, 356, 624–627; (e) Sumby, C. J.; Doonan, C. J. et al., Angew. Chem. Int. Ed., 2017, 129, 8532–8536;
[5] (a) Leyva-Pérez, A.; Corma, A.; Armentano, D.; Pardo, E. J. et al., Angew. Chem. Int. Ed., 2018, 57, 6186-6191; (b) Leyva-Pérez, A.; Armentano, D.; Pardo, E. J. et al., Angew. Chem. Int. Ed. 2018, 57, 17094 –17099; (c) Leyva-Pérez, A.; Armentano, D.; Pardo, E. J. et al., J. Am. Chem. Soc. 2018, 140, 8827−8832; (d) Leyva-Pérez, A.; Fernandez, A.; Armentano, D.; Pardo, E.; Ferrando-Soria, J. et al., J. Am. Chem. Soc. 2019, doi:10.1021/jacs.9b03914. .