Barely porous organic cages for hydrogen isotope separation

Liu, Ming; Zhang, Linda; Little, Marc A.; Kapil, Venkat; Ceriotti, Michele; Yang, Siyuan; Ding, Lifeng; Holden, Daniel; Balderas‐Xicohténcatl, Rafael; He, Donglin; Clowes, Rob; Chong, Samantha Y.; Schütz, Gisela; Chen, Linjiang; Hirscher, Michael; Cooper, Andrew I.

doi:10.1126/science.aax7427

Cited by 256 publications

(258 citation statements)

References 97 publications

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“…Controlled host-guest recognition is of crucial importance to biological processes and artificial supramolecular systems alike. [1,2] Cage-like compounds have been developed to exploit such host-guest interactions to achieve pollutant remediation, [3] gas storage, [4] anion binding, [5] biomimetic guest recognition, [6] molecular separations, [7] and nanoparticle templation. [8,9] Advantages of organic cage hosts include their improved solubility over framework materials,m aking them excellent candidates for both liquid-or solid-phase applications.…”

Section: Introductionmentioning

confidence: 99%

Inducing Social Self‐Sorting in Organic Cages To Tune The Shape of The Internal Cavity

et al. 2020

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Many interesting target guest molecules have low symmetry, yet most methods for synthesising hosts result in highly symmetrical capsules. Methods of generating lower symmetry pores are thus required to maximise the binding affinity in host–guest complexes. Herein, we use mixtures of tetraaldehyde building blocks with cyclohexanediamine to access low‐symmetry imine cages. Whether a low‐energy cage is isolated can be correctly predicted from the thermodynamic preference observed in computational models. The stability of the observed structures depends on the geometrical match of the aldehyde building blocks. One bent aldehyde stands out as unable to assemble into high‐symmetry cages‐and the same aldehyde generates low‐symmetry socially self‐sorted cages when combined with a linear aldehyde. We exploit this finding to synthesise a family of low‐symmetry cages containing heteroatoms, illustrating that pores of varying geometries and surface chemistries may be reliably accessed through computational prediction and self‐sorting.

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Section: Introductionmentioning

confidence: 99%

Inducing Social Self‐Sorting in Organic Cages To Tune The Shape of The Internal Cavity

et al. 2020

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“…Among the many methods that have been introduced in the past decade to accelerate the convergence of path integral calculations [26], those that combine path integral molecular dynamics with a generalized Langevin equation [27][28][29] can be applied transparently to empirical, machine learning or first principles simulations. They have been used to evaluate all sorts of thermodynamic properties, including structural observables [30], free energies [31], momentum distributions [28], and quantum kinetic energies [32] with a reduction in computational effort varying between a factor of 5 at ambient conditions to a factor of 100 at cryogenic temperatures [33]. The aggressive thermostatting used to impose quantum fluctuations, however, significantly disrupts the dynamics of the system, and common wisdom is that the calculation of dynamical properties using PIGLET is impossible.…”

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confidence: 99%

Inexpensive modeling of quantum dynamics using path integral generalized Langevin equation thermostats

Kapil

Wilkins

Lan

et al. 2020

The Journal of Chemical Physics

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The properties of molecules and materials containing light nuclei are affected by their quantum mechanical nature. Modelling these quantum nuclear effects accurately requires computationally demanding path integral techniques. Considerable success has been achieved in reducing the cost of such simulations by using generalized Langevin dynamics to induce frequency-dependent fluctuations. Path integral generalized Langevin equation methods, however, have this far been limited to the study of static, thermodynamic properties due to the large perturbation to the system's dynamics induced by the aggressive thermostatting. Here we introduce a post-processing scheme, based on analytical estimates of the dynamical perturbation induced by the generalized Langevin dynamics, that makes it possible to recover meaningful time correlation properties from a thermostatted trajectory. We show that this approach yields spectroscopic observables for model and realistic systems which have an accuracy comparable to much more demanding approximate quantum dynamics techniques based on full path integral simulations.Vibrational spectroscopic techniques -from conventional infrared (IR) and Raman to advanced femtosecond pump-probe [1, 2], sum-frequency generation, second harmonic scattering [3, 4], and multi-dimensional vibrational spectroscopy [5] -are a cornerstone of chemistry [6]. These techniques have a multitude of applications such as the characterization of functional groups in chemical systems [7], the determination of the atomistic mechanisms of phase transitions through insight into chemical environments [8], and identification of unique structural fingerprints of molecular crystals [9]. The use of atomistic simulations for the computation of spectroscopic properties facilitates the interpretation of these experiments and provides support to the characterization of novel materials.Even neglecting effects that go beyond the Born-Oppenheimer (BO) decoupling of electronic and nuclear degrees of freedom, accurate calculations of the vibrational spectra of materials require an explicit treatment of the quantum dynamics of the nuclear degrees of freedom [10] on the electronic ground state potential energy surface. Quantum dynamics is in principle exactly obtained from the solution of the time dependent Schrödinger equation for the nuclei, but this is only practical for systems containing a handful of degrees of freedom [11,12]. Condensed phase systems can be studied [13] either by an exact treatment of the quantum dynamics of a subset of the nuclear degrees of freedom [14], or through classical dynamics on the quantum free energy surface of the nuclei [15,16]. Among the methods in the latter class, several of the most popular ones are based on the imaginary time path integral framework -such as (thermostatted) ring polymer molecular dynamics [17,18] ((T)RPMD), centroid molec- * venkat.kapil@epfl.ch ular dynamics [19,20] (CMD) and the recently developed quasi-centroid molecular dynamics [21] (QCMD). These methods ignore real time cohe...

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“…The molecular structure of POCs also facilitates post‐synthetic modifications where more robust and intricate cages can be obtained . This strategy has been used to synthesize binding sites in a POC for molecular recognition and for constructing POCs capable of hydrogen isotope separation . Of particular interest to our electrocatalysis program in water is the development of a porphyrin POC that is resistant to hydrolytic decomposition, which we have used to create a porous iron porphyrin catalyst for CO 2 reduction where the permanent porosity increases the density of electrochemically‐active sites for catalysis as well as transport of gaseous substrates and products …”

Section: Methodsmentioning

confidence: 99%

Supramolecular Tuning Enables Selective Oxygen Reduction Catalyzed by Cobalt Porphyrins for Direct Electrosynthesis of Hydrogen Peroxide

et al. 2020

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We report a supramolecular strategy for promoting the selective reduction of O2 for direct electrosynthesis of H2O2. We utilized cobalt tetraphenylporphyrin (Co‐TPP), an oxygen reduction reaction (ORR) catalyst with highly variable product selectivity, as a building block to assemble the permanently porous supramolecular cage Co‐PB‐1(6) bearing six Co‐TPP subunits connected through twenty‐four imine bonds. Reduction of these imine linkers to amines yields the more flexible cage Co‐rPB‐1(6). Both Co‐PB‐1(6) and Co‐rPB‐1(6) cages produce 90–100 % H2O2 from electrochemical ORR catalysis in neutral pH water, whereas the Co‐TPP monomer gives a 50 % mixture of H2O2 and H2O. Bimolecular pathways have been implicated in facilitating H2O formation, therefore, we attribute this high H2O2 selectivity to site isolation of the discrete molecular units in each supramolecule. The ability to control reaction selectivity in supramolecular structures beyond traditional host–guest interactions offers new opportunities for designing such architectures for a broader range of catalytic applications.

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Barely porous organic cages for hydrogen isotope separation

Cited by 256 publications

References 97 publications

Inducing Social Self‐Sorting in Organic Cages To Tune The Shape of The Internal Cavity

Inducing Social Self‐Sorting in Organic Cages To Tune The Shape of The Internal Cavity

Inexpensive modeling of quantum dynamics using path integral generalized Langevin equation thermostats

Supramolecular Tuning Enables Selective Oxygen Reduction Catalyzed by Cobalt Porphyrins for Direct Electrosynthesis of Hydrogen Peroxide

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