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Jinchong Tan - One of the best experts on this subject based on the ideXlab platform.

  • framework flexibility of zif 8 under liquid intrusion discovering time dependent mechanical response and structural relaxation
    Physical Chemistry Chemical Physics, 2018
    Co-Authors: Yueting Sun, Jinchong Tan
    Abstract:

    The structural flexibility of a topical zeolitic imidazolate framework with sodalite topology, termed ZIF-8, has been elucidated through liquid intrusion under moderate pressures (i.e. tens of MPa). By tracking the evolution of water intrusion pressure under cyclic conditions, we interroGate the role of the Gate-Opening mechanism controlling the size variation of the pore channels of ZIF-8. Interestingly, we demonstrate that its channel deformation is recoverable through structural relaxation over time, hence revealing the viscoelastic mechanical response in ZIF-8. We propose a simple approach employing a glycerol–water solution mixture, which can significantly enhance the sensitivity of intrusion pressure for the detection of structural deformation in ZIF-8. By leveraging the time-dependent Gate-Opening phenomenon in ZIF-8, we achieved a notable improvement (50%) in energy dissipation during multicycle mechanical deformation experiments.

  • Liquid Intrusion into Zeolitic Imidazolate Framework‑7 Nanocrystals: Exposing the Roles of Phase Transition and Gate Opening to Enable Energy Absorption Applications
    2018
    Co-Authors: Yueting Sun, Jinchong Tan
    Abstract:

    Liquid intrusion into zeolitic imidazolate framework 7 (ZIF-7) has been observed for the first time. Among the three typical phases of ZIF-7, we discover that only the guest-free ZIF-7-II structure can be intruded by mechanical pressure, and intriguingly, this pressurized liquid intrusion behavior is detected only in nanocrystals, indicating the crystal size effect. Because of its unique combination of non-outflow property and high intrusion pressure, water intrusion into ZIF-7-II generates a marked energy dissipation capacity of ∼2 J/g despite its limited pore volume. We present several strategies that can be easily implemented to tune its intrusion pressure and energy dissipation and accomplish material reusability. Remarkably, we found that the pore cavities of ZIF-7-II can accommodate water molecules without experiencing any phase transition, which is entirely different from other solvents whose incorporation will trigger a spontaneous conversion into ZIF-7-I. Our pressure-vs-volume data further reveal that the process of water infiltration and retainment is controlled by the Gate-Opening/closing mechanism, which has enabled us to probe the viscoelasticity of ZIF-7 via cyclic liquid intrusion experiments. This study has deepened our understanding of the time-dependent mechanical properties of ZIFs and shed new light on the structural flexibility central to the novel applications of metal–organic framework materials

  • identifying the role of terahertz vibrations in metal organic frameworks from Gate Opening phenomenon to shear driven structural destabilization
    Physical Review Letters, 2014
    Co-Authors: Matthew R Ryder, Bartolomeo Civalleri, Thomas D Bennett, Sebastian Henke, Svemir Rudic, Gianfelice Cinque, Felix Fernandezalonso, Jinchong Tan
    Abstract:

    We present an unambiguous identification of low-frequency terahertz vibrations in the archetypal imidazole-based metal-organic framework (MOF) materials: ZIF-4, ZIF-7, and ZIF-8, all of which adopt a zeolite-like nanoporous structure. Using inelastic neutron scattering and synchrotron radiation far-infrared absorption spectroscopy, in conjunction with density functional theory (DFT), we have pinpointed all major sources of vibrational modes. Ab initio DFT calculations revealed the complex nature of the collective THz modes, which enable us to establish detailed correlations with experiments. We discover that low-energy conformational dynamics offers multiple pathways to elucidate novel physical phenomena observed in MOFs. New evidence demonstrates that THz modes are intrinsically linked, not only to anomalous elasticity underpinning Gate-Opening and pore-breathing mechanisms, but also to shear-induced phase transitions and the onset of structural instability.

Rajamani Krishna - One of the best experts on this subject based on the ideXlab platform.

  • tuning Gate Opening of a flexible metal organic framework for ternary gas sieving separation
    Angewandte Chemie, 2020
    Co-Authors: Qiubing Dong, Xin Zhang, Shuang Liu, Ruibiao Lin, Yanan Guo, Akira Yonezu, Rajamani Krishna, Gongpin Liu, Jingui Duan, Ryotaro Matsuda
    Abstract:

    In comparison with the fast development of binary mixture separations, ternary mixture separations are significantly more difficult and have rarely been realized by a single material. Herein, a new strategy of tuning the Gate-Opening pressure of flexible MOFs is developed to tackle such a challenge. As demonstrated by a flexible framework NTU-65, the Gate-Opening pressure of ethylene (C2 H4 ), acetylene (C2 H2 ), and carbon dioxide (CO2 ) can be regulated by temperature. Therefore, efficient sieving separation of this ternary mixture was realized. Under optimized temperature, NTU-65 adsorbed a large amount of C2 H2 and CO2 through Gate-Opening and only negligible amount of C2 H4 . Breakthrough experiments demonstrated that this material can simultaneously capture C2 H2 and CO2 , yielding polymer-grade (>99.99 %) C2 H4 from single breakthrough separation.

  • guest dependent pressure induced Gate Opening effect enables effective separation of propene and propane in a flexible mof
    Chemical Engineering Journal, 2018
    Co-Authors: Rajamani Krishna, Xiaoqing Wang, Bin Wang, Yongzheng Zhang
    Abstract:

    Abstract Propene (C3H6)/propane (C3H8) separation is an important but challenging industrial task. Adsorptive separation using porous materials tends to be an energy- and cost-effective strategy. In this work, a flexible porous MOF named NJU-Bai8 is demonstrated to be a promising adsorbent for the effective separation of C3H6 and C3H8 in a wide temperature range from 298 to 348 K due to its flexible microporous structure, which provides unique guest responsive molecule accommodation. Adsorption isotherms, ideal adsorbed solution theory (IAST) prediction of separation ability, and transient breakthrough on both simulation and experiment were performed to evaluate its separation selectivity and cycling experiments were carried out to explore its structural stability. It was found that the C3H6/C3H8 uptake ratio and IAST selectivity of NJU-Bai8 is 43.2 and 4.6 at 298 K and 20 kPa, respectively. The breakthrough time interval for C3H6 and C3H8 is over 10 min for a C3H6/C3H8/He (20%/20%/60%) mixture under ambient conditions, and this separation ability can maintain more than 10 cycles. Detailed analysis reveals that a guest-dependent pressure induced Gate-Opening effect in the flexible framework of this MOF is indeed responsible for the observed unique selective adsorption and separation performances. This material also shows good regenerability, being favorable for possible industrial application.

  • flexible metal organic frameworks with discriminatory Gate Opening effect for the separation of acetylene from ethylene acetylene mixtures
    European Journal of Inorganic Chemistry, 2016
    Co-Authors: Rajamani Krishna, Yong Wang, Xiaoqing Wang, Jiangfeng Yang
    Abstract:

    Adsorptive separation of acetylene from ethylene/acetylene mixtures is a technologically very important and highly challenging task. In this work, we describe two flexible metal–organic frameworks (MOFs), ELM-11 and ELM-13, that display adsorbate discriminatory Gate effects. The two MOFs exhibit Gate-Opening-type adsorption properties for C2H2 but not for C2H4, leading to a highly selective adsorption of acetylene over ethylene at 273–298 K. The potential of the flexible MOFs for the separation is established by combining measurements of adsorption isotherms, ideal adsorbed solution theory (IAST) calculations of the adsorption equilibrium of the mixture, and transient breakthrough experiments. The results suggest the potential of both flexible MOFs for the industrial removal of acetylene from ethylene/acetylene mixtures through the energy-efficient adsorption separation process.

  • exploiting the Gate Opening effect in a flexible mof for selective adsorption of propyne from c1 c2 c3 hydrocarbons
    Journal of Materials Chemistry, 2016
    Co-Authors: Rajamani Krishna, Yong Wang, Jiangfeng Yang, Xiaoqing Wang
    Abstract:

    The separation of propyne from light hydrocarbon mixtures is of technological importance but poses considerable technical challenges. This article reports on the potential of a flexible metal–organic framework [Cu(dhbc)2(4,4′-bipy)], with Gate-Opening characteristics, that exhibits adsorption selectivity in favor of propyne in a C1/C2/C3 mixture of hydrocarbons. The separation potential of the flexible MOF is established using a judicious combination of measurements of unary isotherms, IAST calculations of mixture adsorption equilibrium, transient breakthrough simulations, along with transient breakthrough experiments. Our multi-tier investigation strategy confirms that propyne can be selectively adsorbed from C1/C2/C3 hydrocarbons in fixed bed adsorbers that are commonly employed in the process industries.

  • utilizing the Gate Opening mechanism in zif 7 for adsorption discrimination between n2o and co2
    Journal of Physical Chemistry C, 2014
    Co-Authors: Deli Chen, Ningwei Wang, Fangfang Wang, Jianwu Xie, Yijun Zhong, Weidong Zhu, Karl J Johnson, Rajamani Krishna
    Abstract:

    N2O is a greenhouse gas with tremendous global warming potential, and more importantly it also causes ozone depletion; thus, the separation of N2O from industrial processes has gained significant attention. We have demonstrated that N2O can be selectively separated from CO2 using the zeolite imidazolate framework ZIF-7. The adsorption/desorption isotherms of both N2O and CO2 in ZIF-7 indicate the Gate-Opening mechanism of this material, and surprisingly, the threshold pressure for the Gate Opening with N2O is lower than that with CO2. Theoretical calculations indicate that both gas–host and gas–gas interaction energies for N2O are more favorable than those for CO2, giving rise to the difference in the threshold pressure between N2O and CO2 in ZIF-7. Breakthrough experiments for N2O/CO2 mixtures confirm that ZIF-7 is capable of separating N2O and CO2 mixtures under the optimized conditions, in reasonable agreement with simulation results, making it a promising material for industrial applications.

Banglin Chen - One of the best experts on this subject based on the ideXlab platform.

  • separation of c2 c1 hydrocarbons through a Gate Opening effect in a microporous metal organic framework
    CrystEngComm, 2017
    Co-Authors: Ruibiao Lin, Rong Guang Lin, Hadi D Arman, Banglin Chen
    Abstract:

    A flexible metal–organic framework (MOF) [Mn(INA)2]·MeOH (1) (INA− = isonicotinate) has been solvothermally synthesized. Single-crystal X-ray diffraction reveals that compound 1 features a 3D microporous framework containing one-dimensional channels. The activated phase 1a displays permanent porosity with a Brunauer–Emmett–Teller (BET) surface area of 236 m2 g−1. Gas sorption analyses reveal that 1a exhibits interesting Gate-Opening hydrocarbon sorption behavior with considerable C2 uptake capacities but a negligible amount for CH4 under ambient conditions. Selectivity calculation and breakthrough experiment comprehensively demonstrate that 1a has remarkably high selectivity towards C2 hydrocarbons over CH4 under ambient conditions.

  • potential of microporous metal organic frameworks for separation of hydrocarbon mixtures
    Energy and Environmental Science, 2016
    Co-Authors: R Krishna, Zongbi Bao, Ganggang Chang, Huabin Xing, Qilong Ren, Banglin Chen
    Abstract:

    In the process industries, the separation of mixtures of hydrocarbons is important both for the preparation of feedstocks and for use as end products. The constituents, hydrocarbons, are either aliphatic or aromatic, saturated or unsaturated, with a large variation in the number of carbon atoms. Using microporous metal–organic frameworks (MOFs), a number of different separation strategies can be employed to achieve the desired separation performance. The strategies include selective binding with the metal atoms of the framework, exploiting differences in molecular packing efficiencies within the ordered pore structures, utilizing selectivities based on the framework flexibility and Gate-Opening mechanisms, and molecular sieving. Various strategies are discussed in this article, along with perspectives for future research and development for improving the separation performance.

Freek Kapteijn - One of the best experts on this subject based on the ideXlab platform.

  • understanding the anomalous alkane selectivity of zif 7 in the separation of light alkane alkene mixtures
    Chemistry: A European Journal, 2011
    Co-Authors: Johan Van Den Bergh, Evgeny A Pidko, Emiel J M Hensen, Canan Gucuyener, Jorge Gascon, Freek Kapteijn
    Abstract:

    C2 and C3 alkanes are selectively adsorbed from mixtures over the corresponding alkenes on the zeolite imidazolate framework ZIF-7 through a Gate-Opening mechanism. As a result, the direct production of the pure alkene upon adsorption and the pure alkane upon desorption in packed columns is possible. Herein, a detailed investigation of the step-wise adsorption and separation of alkanes and alkenes is presented, together with a rigorous performance assessment. A molecular picture of the Gate-Opening mechanism underlying the unprecedented selectivity towards alkane adsorption is proposed based on DFT calculations and a thermodynamic analysis of the adsorption–desorption isotherms.

  • ethane ethene separation turned on its head selective ethane adsorption on the metal organic framework zif 7 through a Gate Opening mechanism
    Journal of the American Chemical Society, 2010
    Co-Authors: Canan Gucuyener, Johan Van Den Bergh, Jorge Gascon, Freek Kapteijn
    Abstract:

    Ethane is selectively adsorbed over ethylene in their mixtures on the zeolite imidazolate framework ZIF-7. In packed columns, this results in the direct production of pure ethylene. This gas-phase separation is attributed to a Gate-Opening effect in which specific threshold pressures control the uptake and release of individual molecules. These threshold pressures differ for the different molecules, leaving a window of selective uptake operation. This phenomenon makes ZIF-7 a perfect candidate for the separation of olefins from paraffins, since in contrast to most microporous materials, the paraffin is selectively adsorbed. Mixture adsorption, as studied by breakthrough experiments, demonstrates that Gate-Opening effects can be effectively used to separate molecules of very similar size.

David Farrusseng - One of the best experts on this subject based on the ideXlab platform.

  • Guest-Induced Gate Opening and Breathing Phenomena in Soft Porous Crystals: Building Thermodynamically Consistent Isotherms
    Journal of Physical Chemistry C, 2012
    Co-Authors: Marc Pera-titus, David Farrusseng
    Abstract:

    Metal organic-frameworks (MOFs) have emerged as a novel and fascinating family of porous materials offering promising perspectives for designing tailor-made adsorbents and catalysts. Particularly, great attention has been paid to flexible nanoporous MOFs (or Soft Porous Crystals) displaying structural phase transitions promoted by external stimuli. This is the case of guest-induced structural transitions upon adsorption being at the origin of the striking Gate Opening and breathing phenomena. We present here a short overview of the formulation of thermodynamic isotherms for describing S-shaped adsorption/desorption curves typical of such phenomena, as well as recent thermodynamic methods for estimating phase transition energies. These methods might be valuable for the rational design of Gate Opening/breathing MOFs.

  • Guest-induced Gate-Opening of a zeolite imidazolate framework
    New Journal of Chemistry, 2011
    Co-Authors: Sonia Aguado, G??rard Bergeret, Carlos Nieto-draghi, Virginie Moizan, Nicolas Bats, Marc Pera-titus, David Farrusseng
    Abstract:

    The zinc benzimidazolate coordination polymer (ZIF-7) shows a reversible Gate-Opening effect upon variation of partial pressure of CO2 or temperature. This phenomenon, which is unique for a MOF with sodalite topology, arises from a phase-to-phase transformation upon guest adsorption-desorption.