Much attention has recently been focused flexible metal-organic frameworks (MOFs), or Soft Porous Crystals, that behave in a remarkable stimuli-responsive fashion upon guest adsorption, temperature, or mechanical pressure. It was shown that these different stimuli-driven structural transitions can be rationalized by combining an understanding of adsorption thermodynamics and mechanical properties of the host phases. [1,2] We show how the combination of a large range of molecular simulation methods can assess the extent of flexibility of known MOF structures, as well as give physical insight into their deformation mechanisms, and predict the occurrence of new phases. In particular, we demonstrate the breathing nature of recently synthesized MOFs CAU-13 and NOTT-300, [3] that had not been observed experimentally (but, for CAU-13, confirmed experimentally since our publication), as well as the occurrence of a rare pressure-induced proton jump transition in the ZAG family.[4] We also show how molecular simulation sheds light into the mechanical properties of stiffer materials, such as the pure-silica zeolites, through the first systematic study of the mechanical properties of 121 pure silica frameworks. [5] By analysis of the elasticity of these 121 zeolites, and the links between framework topology and mechanical properties, we propose to extend the ‘‘feasibility’’ criterion proposed in earlier literature to include elastic anisotropy, allowing to further reduce the number of possible targets for synthesis of SiO2 polymorphs. [1] A. U. Ortiz, A. Boutin, A. H. Fuchs and F.-X. Coudert, Phys. Rev. Lett., 2012, 109, 195502 [2] F.-X. Coudert, C. Mellot-Draznieks, A. H. Fuchs and A. Boutin, J. Am. Chem. Soc., 2009, 131 (10), 3442–3443 [3] A. U. Ortiz, A. Boutin and F.-X. Coudert, Chem. Commun., 2014, 50, 5867–5870. [4] A. U. Ortiz, A. Boutin, K. J. Gagnon, A. Clearfield and F.-X. Coudert, J. Am. Chem. Soc., 2014, 136, 11540–11545. [5] F.-X. Coudert, Phys. Chem. Chem. Phys., 2013, 15, 16012–1601

Assessing and predicting flexibility in framework materials with molecular simulation: MOFs, zeolites, and molecular frameworks

249th National Meeting (2015)

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