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We show here that machine learning is a powerful new tool for predicting the elastic response of zeolites. We built our machine learning approach relying on geometric features only, which are related to local geometry, structure, and porosity of a zeolite, to predict bulk and shear moduli of zeolites with an accuracy exceeding that of force field approaches. The development of this model has illustrated clear correlations between characteristic features of a zeolite and elastic moduli, providing exceptional insight into the mechanics of zeolitic frameworks. Finally, we employ this methodology to predict the elastic response of 590448 hypothetical zeolites, and the results of this massive database provide clear evidence of stability trends in porous materials. [ABSTRACT FROM AUTHOR]

We present here the computational chemistry methods our group uses to investigate the physical and chemical properties of nanoporous materials and adsorbed fluids. We highlight the multiple time and length scales at which these properties can be examined and discuss the computational tools relevant to each scale. Furthermore, we include the key points to consider upsides, downsides, and possible pitfalls for these methods. [ABSTRACT FROM AUTHOR]

The recently reported process of chiral induction in a metal-organic framework (MOF) by nonchiral guest adsorption, demonstrated on the prototypical MOF-5, may revolutionize the production of MOFs for enantioselective separation and catalysis. Herein, we describe an investigation employing multiscale molecular simulation to discover the microscopic mechanism of chiral induction and investigate the stability of the resulting framework. Our results explain how the molecular size and chemical nature of N-methyl-2-pyrrolidone (NMP) give rise to the chiral transformation in MOF-5, whereas it cannot occur for other guest molecules, such as N,N-dimethylformamide (DMF). Moreover, we show that the guest-free CMOF-5 structure is energetically unstable, with either the achiral conventional structure or a closed pore structure preferred, demonstrating that chirality will not be retained upon activation of CMOF-5. While this limits the usability of chiral induction in MOFs, our study opens new avenues for the use of other guest molecules and provides microscopic insight into this unexpected outcome of guest-framework interactions in a soft porous crystal. [ABSTRACT FROM AUTHOR]

Coordination polymers and discrete metallo-supramolecularassembliesof hexaaryl[3]radialene compounds exhibit intriguing structures withshort anion to π-centroid distances in the solid-state. Furthermore,these [3]radialene compounds display useful photophysical and electrochemicalproperties that make them ideal as potential platforms for anion receptors.In this study, hexafluoro[3]radialene was optimized to the MP2/aug-cc-pVTZlevel of theory, and its complexes with halide anions were optimizedto HF/6-31G++(d,p), MP2/6-31G++(d,p), M06-2X/6-31G++(d,p), and M06-2X/6-311G++(d,p)levels of theory. Hexafluoro[3]radialene was shown to have properties(large positive Qzzandareas of positive electrostatic surface potential) comparable to othercompounds that show anion−π interactions. The interactionenergies of complexes of hexafluoro[3]radialene with halide anionswere calculated and found to be favorable and equivalent to thoseof fluorinated aromatic compounds. A series of synthetically accessiblehexaaryl[3]radialenes were optimized to HF/6-31G++(d,p) theory andtheir complexes with halides optimized to the M06-2X/6-31G++(d,p)level of theory. The calculated properties of the electron-deficienthexaaryl[3]radialenes also show large positive Qzzquadrupole moments and two areas of positive potential; atthe [3]radialene core and the acidic aryl hydrogen atoms. The interactionenergies of the complexes of hexaaryl[3]radialenes and halide anionswere found to follow the trend F–> Cl–≈ Br–and correlate with the electron-deficientnature of the [3]radialene. Close contacts were observed between theanion and the radialene core and the aryl hydrogen atoms, suggestinga combination of anion−π and hydrogen bonding is important.Mass spectrometry was used to experimentally observe the complexesof a number of hexaaryl[3]radialenes with F–, Cl–, and Br–predicted computationally.Anion–[3]radialene complexes were successfully detected, andthe stability of the complexes in tandem MS/MS experiments was foundto support the computational results. [ABSTRACT FROM AUTHOR]

A highly porous metal-organic framework DUT-48, isoreticular to DUT-49, is reported with a high surface area of 4560 m 2 ·g -1 and methane storage capacity up to 0.27 g·g -1 (164 cm 3 ·cm -3 ) at 6.5 MPa and 298 K. The flexibility of DUT-48 and DUT-49 under external and internal (adsorption-induced) pressure is analyzed and rationalized using a combination of advanced experimental and computational techniques. While both networks undergo a contraction by mechanical pressure, only DUT-49 shows adsorption-induced structural transitions and negative gas adsorption of n -butane and nitrogen. This adsorption behavior was analyzed by microcalorimetry measurements and molecular simulations to provide an explanation for the lack of adsorption-induced breathing in DUT-48. It was revealed that for DUT-48, a significantly lower adsorption enthalpy difference and a higher framework stiffness prevent adsorption-induced structural transitions and negative gas adsorption. The mechanical behavior of both DUT-48 and DUT-49 was further analyzed by mercury porosimetry experiments and molecular simulations. Both materials exhibit large volume changes under hydrostatic compression, demonstrating noteworthy potential as shock absorbers with unprecedented high work energies., Competing Interests: The authors declare no competing financial interest.

Soft microporous materials exhibit properties, such as gated adsorption and breathing, which are highly desirable for many applications. These properties are largely studied for single crystals; however, many potential applications expect to construct structured or composite systems, examples of which include monoliths and mixed-matrix membranes. Herein, we use finite element methods to predict the macroscopic mechanical response of composite microporous materials. This implementation connects the microscopic treatment of crystalline structures to the response of a macroscopic sample. Our simulations reveal the bulk modulus of an embedded adsorbent within a composite is affected by the thickness and properties of the encapsulating layer. Subsequently, we employ this methodology to examine mixed-matrix membranes and materials of negative linear compressibility. This application of finite element methods allows for unprecedented insight into the mechanical properties of real-world systems and supports the development of composites containing mechanically anomalous porous materials.