S.M.J. Rogge

Interfacial study of clathrates confined in reversed silica pores

P. M. Mileo, S.M.J. Rogge, M. Houlleberghs, E. Breynaert, J.A. Martens, V. Van Speybroeck
Journal of Materials Chemistry A
2021
A1

Abstract 

Storing methane in clathrates is one of the most promising alternatives for transporting natural gas (NG) as it offers similar gas densities as liquefied and compressed NG while offering lower safety risks. However, the practical use of clathrates is limited given the extremely low temperatures and high pressures necessary to form these structures. Therefore, it has been suggested to confine clathrates in nanoporous materials, as this can relent clathrate’s formation conditions while preserving its CH4 volumetric storage. Yet, the choice of nanoporous materials to be employed as clathrate growing platform is still rather arbitrary. Herein, we tackle this challenge in a systematic way by computationally exploring the stability of clathrates confined in alkyl-grafted silica materials with different pore sizes, ligand densities and ligand types. Based on our findings we are able to propose key design criteria for nanoporous materials favoring the stability of a neighbouring clathrate phase, namely large pore sizes, high ligand densities, and smooth pore walls. We hope the atomistic insight provided in this work will guide and facilitate the development of new nanomaterials designed to promote the formation of clathrates.

Large-Scale Molecular Dynamics Simulations Reveal New Insights Into the Phase Transition Mechanisms in MIL-53(Al)

S. Vandenhaute, S.M.J. Rogge, V. Van Speybroeck
Frontiers in Chemistry
9: 699
2021
A1

Abstract 

Soft porous crystals have the ability to undergo large structural transformations upon exposure to external stimuli while maintaining their long-range structural order, and the size of the crystal plays an important role in this flexible behavior. Computational modeling has the potential to unravel mechanistic details of these phase transitions, provided that the models are representative for experimental crystal sizes and allow for spatially disordered phenomena to occur. Here, we take a major step forward and enable simulations of metal-organic frameworks containing more than a million atoms. This is achieved by exploiting the massive parallelism of state-of-the-art GPUs using the OpenMM software package, for which we developed a new pressure control algorithm that allows for fully anisotropic unit cell fluctuations. As a proof of concept, we study the transition mechanism in MIL-53(Al) under various external pressures. In the lower pressure regime, a layer-by-layer mechanism is observed, while at higher pressures, the transition is initiated at discrete nucleation points and temporarily induces various domains in both the open and closed pore phases. The presented workflow opens the possibility to deduce transition mechanism diagrams for soft porous crystals in terms of the crystal size and the strength of the external stimulus.

Gold Open Access

Hydrogen Clathrates: Next Generation Hydrogen Storage Materials

A. Gupta, G.V. Baron, P. Perreault, S. Lenaerts, R.-G. Ciocarlan, P. Cool, P. M. Mileo, S.M.J. Rogge, V. Van Speybroeck, G. Watson, P. Van der Voort, M. Houlleberghs, E. Breynaert, J.A. Martens, J.F.M. Denayer
Energy Storage Materials
41, 69-107
2021
A1

Abstract 

Extensive research has been carried on the molecular adsorption in high surface area materials such as carbonaceous materials and MOFs as well as atomic bonded hydrogen in metals and alloys. Clathrates stand among the ones to be recently suggested for hydrogen storage. Although, the simulations predict lower capacity than the expected by the DOE norms, the additional benefits of clathrates such as low production and operational cost, fully reversible reaction, environmentally benign nature, low risk of flammability make them one of the most promising materials to be explored in the next decade. The inherent ability to tailor the properties of clathrates using techniques such as addition of promoter molecules, use of porous supports and formation of novel reverse micelles morphology provide immense scope customisation and growth. As rapidly evolving materials, clathrates promise to get as close as possible in the search of “holy grail” of hydrogen storage. This review aims to provide the audience with the background of the current developments in the solid-state hydrogen storage materials, with a special focus on the hydrogen clathrates. The in-depth analysis of the hydrogen clathrates will be provided beginning from their discovery, various additives utilised to enhance their thermodynamic and kinetic properties, challenges in the characterisation of hydrogen in clathrates, theoretical developments to justify the experimental findings and the upscaling opportunities presented by this system. The review will present state of the art in the field and also provide a global picture for the path forward.

Gold Open Access

Towards modeling spatiotemporal processes in metal–organic frameworks

V. Van Speybroeck, S. Vandenhaute, A.E.J. Hoffman, S.M.J. Rogge
Trends in Chemistry
3 (8): 605-619
2021
A1

Abstract 

Metal–organic frameworks (MOFs) are hybrid materials constructed from metal clusters linked by organic linkers, which can be engineered for target functional applications in, for example, catalysis, sensing, and storage. The dynamic response of MOFs on external stimuli can be tuned by spatial heterogeneities such as defects and crystal size as well as by operating conditions such as temperature, pressure, moisture, and external fields. Modeling the spatiotemporal evolution of MOFs under operating conditions and at length and time scales comparable with experimental observations is extremely challenging. Herein, we give a status on the modeling of spatiotemporal processes in MOFs under working conditions and reflect on how modeling can be reconciled with in situ spectroscopy measurements.

Gold Open Access

High-rate nanofluidic energy absorption in porous zeolitic frameworks

Y. Sun, S.M.J. Rogge, A. Lamaire, S. Vandenbrande, J. Wieme, C.R. Siviour, V. Van Speybroeck, J.-C. Tan
Nature Materials
20 (7), 1015–1023
2021
A1

Abstract 

Optimal mechanical impact absorbers are reusable and exhibit high specific energy absorption. The forced intrusion of liquid water in hydrophobic nanoporous materials, such as zeolitic imidazolate frameworks (ZIFs), presents an attractive pathway to engineer such systems. However, to harness their full potential, it is crucial to understand the underlying water intrusion and extrusion mechanisms under realistic, high-rate deformation conditions. Here, we report a critical increase of the energy absorption capacity of confined water-ZIF systems at elevated strain rates. Starting from ZIF-8 as proof-of-concept, we demonstrate that this attractive rate dependence is generally applicable to cage-type ZIFs but disappears for channel-containing zeolites. Molecular simulations reveal that this phenomenon originates from the intrinsic nanosecond timescale needed for critical-sized water clusters to nucleate inside the nanocages, expediting water transport through the framework. Harnessing this fundamental understanding, design rules are formulated to construct effective, tailorable and reusable impact energy absorbers for challenging new applications.

Chlorination of a Zeolitic-Imidazolate Framework Tunes Packing and van der Waals Interaction of Carbon Dioxide for Optimized Adsorptive Separation

L.H. Wee, S. Vandenbrande, S.M.J. Rogge, J. Wieme, K. Asselman, E. Jardim, J. Silvestre-Albero, J. Navarro, V. Van Speybroeck, J.A. Martens, C. Kirschhock
JACS (Journal of the American Chemical Society)
143 (13), 4962-4968
2021
A1

Abstract 

Molecular separation of carbon dioxide (CO2) and methane (CH4) is of growing interest for biogas upgrading, carbon capture and utilization, methane synthesis and for purification of natural gas. Here, we report a new zeolitic-imidazolate framework (ZIF), coined COK-17, with exceptionally high affinity for the adsorption of CO2 by London dispersion forces, mediated by chlorine substituents of the imidazolate linkers. COK-17 is a new type of flexible zeolitic-imidazolate framework Zn(4,5-dichloroimidazolate)2 with the SOD framework topology. Below 200 K it displays a metastable closed-pore phase next to its stable open-pore phase. At temperatures above 200 K, COK-17 always adopts its open-pore structure, providing unique adsorption sites for selective CO2 adsorption and packing through van der Waals interactions with the chlorine groups, lining the walls of the micropores. Localization of the adsorbed CO2 molecules by Rietveld refinement of X-ray diffraction data and periodic density functional theory calculations revealed the presence and nature of different adsorption sites. In agreement with experimental data, grand canonical Monte Carlo simulations of adsorption isotherms of CO2 and CH4 in COK-17 confirmed the role of the chlorine functions of the linkers and demonstrated the superiority of COK-17 compared to other adsorbents such as ZIF-8 and ZIF-71.

Gold Open Access

Quantifying the likelihood of structural models through a dynamically enhanced powder X‐ray diffraction protocol

S. Borgmans, S.M.J. Rogge, J. De Vos, C.V. Stevens, P. Van der Voort, V. Van Speybroeck
Angewandte Chemie int. Ed.
60 (16), 8913-8922
2021
A1

Abstract 

Structurally characterizing new materials is tremendously challenging, especially when single crystal structures are hardly available which is often the case for covalent organic frameworks. Yet, knowledge of the atomic structure is key to establish structure‐function relations and enable functional material design. Herein a new protocol is proposed to unambiguously predict the structure of poorly crystalline materials through a likelihood ordering based on the X‐ray diffraction (XRD) pattern. Key of the procedure is the broad set of structures generated from a limited number of building blocks and topologies, which is submitted to operando structural characterization. The dynamic averaging in the latter accounts for the operando conditions and inherent temporal character of experimental measurements, yielding unparalleled agreement with experimental powder XRD patterns. The proposed concept can hence unquestionably identify the structure of experimentally synthesized materials, a crucial step to design next generation functional materials.

Gold Open Access

Texture Formation in Polycrystalline Thin Films of All-Inorganic Lead Halide Perovskite

J.A. Steele, E. Solano, H. Jin, V. Prakasam, T. Braeckevelt, H. Yuan, Z. Lin, R. de Kloe, Q. Wang, S.M.J. Rogge, V. Van Speybroeck, D. Chernyshov, J. Hofkens, M. Roeffaers
Advanced Materials
33 (13), 2007224
2021
A1

Abstract 

Controlling grain orientations within polycrystalline all-inorganic halide perovskite solar cells can help increase conversion efficiencies toward their thermodynamic limits, however the forces governing texture formation are ambiguous. Using synchrotron X-ray diffraction, we report meso-structure formation within polycrystalline CsPbI2.85Br0.15 powders as they cool from a high-temperature cubic perovskite (α-phase). Tetragonal distortions (β-phase) trigger preferential crystallographic alignment within polycrystalline ensembles, a feature we suggest is coordinated across multiple neighboring grains via interfacial forces that select for certain lattice distortions over others. External anisotropy is then imposed on polycrystalline thin films of orthorhombic (γ-phase) CsPbI3-xBrx perovskite via substrate clamping, revealing two fundamental uniaxial texture formations; (i) I-rich films possess orthorhombic-like texture (<100> out-of-plane; <010> and <001> in-plane), while (ii) Br-rich films form tetragonal-like texture (<110> out-of-plane; <1-10> and <001> in-plane). In contrast to relatively uninfluential factors like the choice of substrate, film thickness and annealing temperature, Br incorporation modifies the γ-CsPbI3-xBrx crystal structure by reducing the orthorhombic lattice distortion (making it more tetragonal-like) and governs the formation of the different, energetically favored textures within polycrystalline thin films.

Strongly Reducing (Diarylamino)benzene Based Covalent Organic Framework for Metal-Free Visible Light Photocatalytic H2O2 Generation

C. Krishnaraj, H. S. Jena, L. Bourda, A. Laemont, P. Pachfule, J. Roeser, C. V. Chandran, S. Borgmans, S.M.J. Rogge, K. Leus, C.V. Stevens, J.A. Martens, V. Van Speybroeck, E. Breynaert, A. Thomas, P. Van der Voort
JACS (Journal of the American Chemical Society)
142 (47), 20107-20116
2020
A1

Abstract 

Photocatalytic reduction of molecular oxygen is a promising route toward sustainable production of hydrogen peroxide (H2O2). This challenging process requires photoactive semiconductors enabling solar energy driven generation and separation of electrons and holes with high charge transfer kinetics. Covalent organic frameworks (COFs) are an emerging class of photoactive semiconductors, tunable at a molecular level for high charge carrier generation and transfer. Herein, we report two newly designed two-dimensional COFs based on a (diarylamino)benzene linker that forms a Kagome (kgm) lattice and shows strong visible light absorption. Their high crystallinity and large surface areas (up to 1165 m2·g−1) allow efficient charge transfer and diffusion. The diarylamine (donor) unit promotes strong reduction properties, enabling these COFs to efficiently reduce oxygen to form H2O2. Overall, the use of a metal-free, recyclable photocatalytic system allows efficient photocatalytic solar transformations.

Gold Open Access

Charting the Metal-Dependent High-Pressure Stability of Bimetallic UiO-66 Materials

S.M.J. Rogge, P.G. Yot, J. Jacobsen, F. Muniz-Miranda, S. Vandenbrande, J. Gosch, V. Ortiz, I. Collings, S. Devautour-Vinot, G. Maurin, N. Stock, V. Van Speybroeck
ACS Materials Letters
2 (4), 438-445
2020
A1

Abstract 

In theory, bimetallic UiO-66(Zr:Ce) and UiO-66(Zr:Hf) metal-organic frameworks (MOFs) are extremely versatile and attractive nanoporous materials as they combine the high catalytic activity of UiO-66(Ce) or UiO-66(Hf) with the outstanding stability of UiO-66(Zr). Using in situ high-pressure powder X-ray diffraction, however, we observe that this expected mechanical stability is not achieved when incorporating cerium or hafnium in UiO-66(Zr). This observation is akin to the earlier observed reduced thermal stability of UiO-66(Zr:Ce) compounds. To elucidate the atomic origin of this phenomenon, we chart the loss-of-crystallinity pressures of 22 monometallic and bimetallic UiO-66 materials and systematically isolate their intrinsic mechanical stability from their defect-induced weakening. This complementary experimental/computational approach reveals that the intrinsic mechanical stability of these bimetallic MOFs decreases nonlinearly upon cerium incorporation but remains unaffected by the zirconium:hafnium ratio. Additionally, all experimental samples suffer from defect-induced weakening, a synthesis-controlled effect that is observed to be independent of their intrinsic stability.

Gold Open Access

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