Center for Molecular Modeling - S. Borgmans

Maximizing Porosity and Water Sorption in Covalent Organic Frameworks via β-Ketoenamine Linkages

sven — Thu, 21 Aug 2025 15:16:32 +0000

R. G. AbdulHalim, B. Garai, J. De Vos, S. Borgmans, L. Gkoura, S. Varghese, F. Benyettou, M. A. Olson, S.M.J. Rogge, A. Trabolsi

SMALL

e08046

2025

Abstract

Controlling the crystallinity and porosity of 2D covalent organic frameworks (2D COFs) is crucial for their applications in science and technology. Herein, the construction of 2D COFs, COF-TP-X, is reported using a multicomponent reaction strategy that introduces β-ketoenamine linkages into isostructural imine-linked COFs. This approach yields materials with exceptional crystallinity, stability, and tunable hydrophilicity. The integration of β-ketoenamine linkages promotes intralayer planarity via NH⋯O hydrogen bonds and enhances π-electronic conjugation within and between layers. By partially substituting (43 mol%) 1,3,5-triformylbenzene with 1,3,5-triformylphloroglucinol, an outstanding gravimetric surface area of 1,984 m² g⁻¹ and a pore volume of 0.8 cm³ g⁻¹ are achieved—a remarkable two-fold increase compared to mono-linker counterparts. Moreover, COF-TP-X exhibits an exceptional water uptake capacity of 0.70 g g⁻¹ (70 wt.%) and superior hydrolytic stability, as confirmed by over 200 cycles of water adsorption–desorption experiments. Furthermore, molecular simulations reveal the significant role of electrostatic interactions between β-ketoenamine linkages in enhancing interlayer stacking and crystallinity. The findings provide key insights into COF design via a mixed-linker strategy, representing a significant advancement in developing COFs with superior performance and paving the way for their industrial applications.

Open Access version available at UGent repository

Gold Open Access

DOI

http://dx.doi.org/10.1002/smll.202508046

Private attachment

main.pdf

High-Throughput Screening of Covalent Organic Frameworks for Carbon Capture Using Machine Learning

sven — Tue, 14 May 2024 14:50:15 +0000

J. De Vos, S. Ravichandran, S. Borgmans, L. Vanduyfhuys, P. Van der Voort, S.M.J. Rogge, V. Van Speybroeck

Chemistry of Materials

36, 9, 4315-4330

2024

Abstract

Postcombustion carbon capture provides a high-potential pathway to reduce anthropogenic CO₂ emissions in the short term. In this respect, nanoporous materials, such as covalent organic frameworks (COFs), offer a promising platform as adsorbent beds. However, due to the modular nature of COFs, an almost unlimited number of structures can possibly be synthesized. To efficiently identify promising materials and reveal performance trends within the COF material space, we present a computational high-throughput screening of 268,687 COFs for their ability to efficiently and selectively separate CO₂ from the flue gas of power plants using a pressure swing adsorption process. Furthermore, we demonstrate that our screening can be significantly accelerated using machine learning to identify a set of promising materials. These are subsequently characterized with high accuracy, taking into account the effects of competitive adsorption and coadsorption. Our screening reveals that imide, (keto)enamine, and (acyl)hydrazone COFs are particularly interesting for carbon capture. Additionally, the best-performing materials are 3D COFs possessing strong CO₂ adsorption sites between aromatic rings at opposite sides of pores with a diameter of 1.0 nm. In 2D COFs, a significant influence of the framework chemistry, such as imide linkages or fluoro groups, is observed. Our design rules can guide experimental researchers to construct high-performing COFs for CO₂ capture.

Gold Open Access

DOI

http://dx.doi.org/10.1021/acs.chemmater.3c03230

Computational Protocol for the Spectral Assignment of NMR Resonances in Covalent Organic Frameworks

leen — Tue, 23 Apr 2024 07:56:25 +0000

S. Vanlommel, S. Borgmans, C. V. Chandran, S. Radhakrishnan, P. Van der Voort, E. Breynaert, V. Van Speybroeck

Journal of Chemical Theory and Computation (JCTC)

20, 9, 3823–3838

2024

Abstract

Solid-state nuclear magnetic resonance spectroscopy is routinely used in the field of covalent organic frameworks to elucidate or confirm the structure of the synthesized samples and to understand dynamic phenomena. Typically this involves the interpretation and simulation of the spectra through the assumption of symmetry elements of the building units, hinging on the correct assignment of each line shape. To avoid misinterpretation resulting from library-based assignment without a theoretical basis incorporating the impact of the framework, this work proposes a first-principles computational protocol for the assignment of experimental spectra, which exploits the symmetry of the underlying building blocks for computational feasibility. In this way, this protocol accommodates the validation of previous experimental assignments and can serve to complement new NMR measurements.

DOI

https://doi.org/10.1021/acs.jctc.3c01414

Private attachment

VANLOM~1.PDF

Engineering of Phenylpyridine- and Bipyridine-Based Covalent Organic Frameworks for Photocatalytic Tandem Aerobic Oxidation/Povarov Cyclization

siebe — Wed, 06 Dec 2023 13:17:04 +0000

M. Debruyne, S. Borgmans, S. Radhakrishnan, E. Breynaert, H. Vrielinck, K. Leus, A. Laemont, J. De Vos, K. S. Rawat, S. Vanlommel, H. Rijckaert, H. Salemi, J. Everaert, F. Vanden Bussche, D. Poelman, R. Morent, N. De Geyter, P. Van der Voort, V. Van Speybroeck, C.V. Stevens

ACS Applied Materials & Interfaces

15, 29, 35092–35106

2023

Abstract

Covalent organic frameworks (COFs) are emerging as a new class of photoactive organic semiconductors, which possess crystalline ordered structures and high surface areas. COFs can be tailor-made toward specific (photocatalytic) applications, and the size and position of their band gaps can be tuned by the choice of building blocks and linkages. However, many types of building blocks are still unexplored as photocatalytic moieties and the scope of reactions photocatalyzed by COFs remains quite limited. In this work, we report the synthesis and application of two bipyridine- or phenylpyridine-based COFs: TpBpyCOF and TpPpyCOF. Due to their good photocatalytic properties, both materials were applied as metal-free photocatalysts for the tandem aerobic oxidation/Povarov cyclization and α-oxidation of N-aryl glycine derivatives, with the bipyridine-based TpBpyCOF exhibiting the highest activity. By expanding the range of reactions that can be photocatalyzed by COFs, this work paves the way toward the more widespread application of COFs as metal-free heterogeneous photocatalysts as a convenient alternative for commonly used homogeneous (metal-based) photocatalysts.

Open Access version available at UGent repository

DOI

http://dx.doi.org/

Private attachment

debruyne-et-al-2023-engineering-of-phenylpyridine-and-bipyridine-based-covalent-organic-frameworks-for-photocatalytic.pdf

am3c07036_si_001 (2).pdf

OGRe: Optimal grid refinement protocol for accurate free energy surfaces and its application to proton hopping in zeolites and 2D COF stacking

leen — Mon, 02 Oct 2023 08:12:55 +0000

S. Borgmans, S.M.J. Rogge, L. Vanduyfhuys, V. Van Speybroeck

Journal of Chemical Theory and Computation

19, 24, 9032-9048

2024

Abstract

While free energy surfaces are the crux of our understanding in many chemical and biological processes, their accuracy is generally unknown. Moreover, many developments to improve their accuracy are often complicated, impeding their general use. Luckily, several tools and guidelines are already in place to identify these shortcomings, but they are typically lacking in flexibility or fail to systematically determine how to improve the accuracy of the free energy calculation. To overcome these limitations, this work introduces OGRe--a python package for optimal grid refinement in an arbitrary number of dimensions. OGRe is based on three metrics which gauge the confinement, consistency, and overlap of each simulation in a series of umbrella sampling (US) simulations, an enhanced sampling technique ubiquitously adopted to construct free energy surfaces for hindered processes. As these three metrics are fundamentally linked to the accuracy of the weighted histogram analysis method, adopted to generate free energy surfaces from US simulations, they facilitate a systematic construction of accurate free energy profiles, where each metric is driven by a specific umbrella parameter. This allows for the derivation of a consistent and optimal collection of umbrellas for each simulation, largely independent of the initial values, thereby dramatically increasing the ease-of-use towards accurate free energy surfaces. As such, OGRe is particularly suited to determined complex free energy surfaces, with large activation barriers and shallow minima, which underpin many physical and chemical transformations, and hence to further our fundamental understanding of these processes.

Gold Open Access

DOI

https://doi.org/10.1021/acs.jctc.3c01028

Private attachment

og-re-optimal-grid-refinement-protocol-for-accurate-free-energy-surfaces-and-its-application-to-proton.pdf

Understanding the phase transition mechanism in the lead halide perovskite CsPbBr₃ via theoretical and experimental GIWAXS and Raman spectroscopy

leen — Thu, 06 Apr 2023 07:27:01 +0000

A.E.J. Hoffman, R.A. Saha, S. Borgmans, P. Puech, T. Braeckevelt, M.B.J. Roeffaers, J.A. Steele, J. Hofkens, V. Van Speybroeck

APL Materials

Volume 11, Issue 4, article number 041124

2023

Abstract

Metal-halide perovskites (MHPs) exhibit excellent properties for application in optoelectronic devices. The bottleneck for their incorporation is the lack of long-term stability such as degradation due to external conditions (heat, light, oxygen, moisture, and mechanical stress), but the occurrence of phase transitions also affects their performance. Structural phase transitions are often influenced by phonon modes. Hence, an insight into both the structure and lattice dynamics is vital to assess the potential of MHPs. In this study, GIWAXS and Raman spectroscopy are applied, supported by density functional theory calculations, to investigate the apparent manifestation of structural phase transitions in the MHP CsPbBr₃. Macroscopically, CsPbBr₃ undergoes phase transitions between a cubic (α), tetragonal (β), and orthorhombic (γ) phase with decreasing temperature. However, microscopically, it has been argued that only the γ phase exists, while the other phases exist as averages over length and time scales within distinct temperature ranges. Here, direct proof is provided for this conjecture by analyzing both theoretical diffraction patterns and the evolution of the tilting angle of the PbBr₆ octahedra from molecular dynamics simulations. Moreover, sound agreement between experimental and theoretical Raman spectra allowed to identify the Raman active phonon modes and to investigate their frequency as a function of temperature. As such, this work increases the understanding of the structure and lattice dynamics of CsPbBr₃ and similar MHPs.

Gold Open Access

DOI

http://dx.doi.org/10.1063/5.0144344

Private attachment

041124_1_5.0144344.pdf

ReDD-COFFEE: A ready-to-use database of covalent organic framework structures and accurate force fields to enable high-throughput screenings

sven — Wed, 22 Mar 2023 00:05:31 +0000

J. De Vos, S. Borgmans, P. Van der Voort, S.M.J. Rogge, V. Van Speybroeck

J. Mater. Chem. A

11, 14, 7468-7487

2023

Abstract

Covalent organic frameworks (COFs) are a versatile class of building block materials with outstanding properties thanks to their strong covalent bonds and low density. Given the sheer number of hypothetical COFs envisioned via reticular synthesis, only a fraction of all COFs have been synthesized so far. Computational high-throughput screenings offer a valuable alternative to speed-up such materials discovery. Yet, such screenings vitally depend on the availability of diverse databases and accurate interatomic potentials to efficiently predict each hypothetical COF’s macroscopic behavior, which is currently lacking. Therefore, we herein present ReDD-COFFEE, the Ready-to-use and Diverse Database of Covalent Organic Frameworks with Force field based Energy Evaluation, containing 268 687 COFs and accompanying ab initio derived force fields that are shown to outperform generic ones. Our structure assembly approach results in a huge amount of computer-ready structures with a high diversity in terms of geometric properties, linker cores, and linkage types. Furthermore, the textural properties of the database are analyzed and the most promising COFs for vehicular methane storage are identified. By making the database freely accessible, we hope it may also inspire others to further explore the potential of these intriguing functional materials.

Gold Open Access

DOI

http://dx.doi.org/10.1039/D3TA00470H

Absorbing stress via molecular crumple zones: Strain engineering flexibility into the rigid UiO-66 material

sven — Mon, 13 Mar 2023 15:58:20 +0000

S.M.J. Rogge, S. Borgmans, V. Van Speybroeck

Matter

6, 5, 1435-1462

2023

Abstract

Nanostructured materials such as metal-organic frameworks and perovskites can be tuned toward applications ranging from sensors to photovoltaic devices. Such design requires causal relations between a material’s atomic structure and macroscopic function, which remain elusive. Therefore, we herein introduce strain engineering as a general approach to rationalizing and designing how atomic-level structural modifications induce dynamically interacting strain fields that dictate a material’s macroscopic mechanical behavior. We first demonstrate the potential of strain engineering by designing shear instabilities in UiO-66, leading to counterintuitive behavior. The strain-engineered structures exhibit time- and space-dependent crumple zones that instill flexibility in the rigid material and locally focus the strain, partially preserving the material’s porosity under compression. Secondly, our strain fields help explain stimulus-induced phase coexistence in the flexible CoBDP, DMOF-1(Zn), and MIL-53(Al)-F materials. These examples demonstrate how strain engineering can be adopted to design state-of-the-art materials for challenging applications from the atomic level onward.

Gold Open Access

DOI

http://dx.doi.org/10.1016/j.matt.2023.02.009

Private attachment

main_unhighlighted.pdf

Exploring the phase stability in interpenetrated diamondoid covalent organic frameworks

sander — Wed, 24 Aug 2022 08:25:13 +0000

S. Borgmans, S.M.J. Rogge, J. De Vos, P. Van der Voort, V. Van Speybroeck

Communications Chemistry

6, 1, 5

2023

Abstract

Soft porous crystals, which are responsive to external stimuli such as temperature, pressure, or gas adsorption, are being extensively investigated for various technological applications. However, while substantial research has been devoted to stimuli-responsive metal-organic frameworks, structural flexibility in 3D covalent organic frameworks (COFs) remains ill-understood, and is almost exclusively found in COFs exhibiting the diamondoid (dia) topology. Herein, we systemically investigate how the structural decoration of these 3D dia COFs—their specific building blocks and degree of interpenetration—as well as external triggers such as temperature and guest adsorption may promote or suppress their phase transformations, as captured by a collection of 2D free energy landscapes. Together, these provide a comprehensive understanding of the necessary conditions to design flexible diamondoid COFs. This study reveals how their flexibility originates from the balance between steric hindrance and dispersive interactions of the structural decoration, thereby providing insight into how new flexible 3D COFs can be designed.

Open Access version available at UGent repository

Gold Open Access

DOI

http://dx.doi.org/10.1038/s42004-022-00808-y

Private attachment

s42004-022-00808-y.pdf

How the Layer Alignment in Two-dimensional Nanoporous Covalent Organic Frameworks Impacts Its Electronic Properties

tbraeckevelt — Sat, 11 Jun 2022 18:58:18 +0000

K. S. Rawat, S. Borgmans, T. Braeckevelt, C.V. Stevens, P. Van der Voort, V. Van Speybroeck

ACS Applied Nano Materials

5, 10, 14377-14387

2022

Abstract

Two-dimensional nanoporous covalent organic frame-works (2D COFs) have gathered significant interest due to their wide range of applications. Due to the lack of strong covalent interlayer interactions, their layers can be stacked in countless ways, each resulting in unique nanoscale characteristics impacting the structural, chemical, and electronic properties. To characterize and understand the layer stacking in 2D COFs and its effect on the structural and electronic properties, we carried out a detailed density functional theory investigation on four materials, CTF-1, COF-1, COF-5, and Pc-PBBA. This entailed an in-depth evaluation of the potential energy as a function of the interlayer distance and offset, the powder X-ray diffraction (PXRD) pattern, and the electronic properties. From the potential energy surfaces, the typical slipped AA-stacking configuration was confirmed as optimal for each of the 2D COFs, with a slight offset from a perfect alignment of the layers. The statically calculated PXRD patterns based on these optimized stacking configurations showed discrepancies when compared to experimental data. Instead, when properly accounting for dynamic fluctuations by calculating the average diffraction pattern over the course of a molecular dynamics simulation, a better agreement with the experiment is obtained. Different stacking configurations also profoundly affected the electronic band structure of COFs as the interlayer pi-pi interactions are significantly impacted by the layer offset. Evidently, with decreasing layer offsets, the pi-pi interactions increase due to the layer alignment, leading to a decrease in the band gap and an increase in interlayer charge mobility. Our study highlights the need for accurate modeling of the stacking configuration in 2D COFs as a small-scale deviation in the adjacent layer position can significantly affect the structural and electronic properties.

DOI

https://doi.org/10.1021/acsanm.2c02647

Private attachment

acsanm.2c02647.pdf