Center for Molecular Modeling - X. Feng

Transforming 2D Imine into 3D Thiazole Covalent Organic Frameworks by Conjugated Connectors: Fully Conjugated Photocatalysts

leen — Tue, 25 Feb 2025 09:15:52 +0000

M. Deng, J. Chakraborty, G. Wang, K. S. Rawat, L. Bourda, J. Sun, I. Nath, Y. Ji, P. Geiregat, V. Van Speybroeck, X. Feng, P. Van der Voort

JACS (Journal of the American Chemical Society)

2025

Abstract

We developed a robust three-dimensional (3D) covalent organic framework (COF), fully conjugated in both the planar (x, y) and interlayer (z) directions, using a one-pot sulfurization process. We converted the two-dimensional (2D) imine-linked COF (Py-BDA-COF) to the 3D thiazole-linked COF (3D-Py-BDA-S-COF). In the interlayer direction (z-axis), the alternating covalently bound acetylene and ethylene arrangements serve as conjugated connectors (“pillars”) and create a fully conjugated and very robust COF in all three dimensions. On top of this, the presence of the sulfur lone pair electrons in the thiazole rings considerably enhances the electron delocalization degree of the frameworks. The 3D-Py-BDA-S-COF is successfully evaluated in the photocatalytic reduction of nitrobenzene.

DOI

http://dx.doi.org/10.1021/jacs.4c15825

Private attachment

deng-et-al-2025.pdf

2025 - Deng - JACS - 147 - 10219-10230.pdf

Engineering a highly defective stable UiO-66 with tunable Lewis-Brønsted acidity - The role of the hemilabile linker

alexander — Tue, 28 Jan 2020 15:56:11 +0000

X. Feng, J. Hajek, H. S. Jena, G. Wang, S. K. P. Veerapandian, R. Morent, N. De Geyter, K. Leyssens, A.E.J. Hoffman, V. Meynen, C. Marquez, D. De Vos, V. Van Speybroeck, K. Leus, P. Van der Voort

JACS (Journal of the American Chemical Society)

142 (6), 3174-3183

2020

Abstract

The stability of metal-organic frameworks (MOFs) typically decreases with an increasing number of defects, limiting the number of defects that can be created and limiting catalytic and other applications. Herein, we use a hemilabile (Hl) linker to create up to maximum 6 defects per cluster in UiO-66. We have synthesized hemilabile UiO-66 (Hl-UiO-66) using benzene dicarboxylate (BDC) as linker and 4-sulfonatobenzoate (PSBA) as the hemilabile linker. The PSBA acts not only as a modulator to create defects, but also as a co-ligand that enhances the stability of the resulting defective framework. Furthermore, upon a post-synthetic treatment in H2SO4, the average number of defects increases to the optimum of six missing BDC linkers per cluster (3 per formula unit), leaving the Zr-nodes on average 6-fold coordinated. Remarkably, the thermal stability of the materials further increases upon this treatment. Periodic density functional theory calculations confirm that the hemilabile ligands strengthen this highly defective structure by several stabilizing interactions. Finally, the catalytic activity of the obtained materials is evaluated in the acid-catalyzed isomerization of α-pinene oxide. This reaction is particularly sensitive to the Brønsted or Lewis acid sites in the catalyst. In comparison to the pristine UiO-66, which mainly possesses Brønsted acid sites, the Hl-UiO-66 and the post-synthetically treated Hl-UiO-66 structures exhibited a higher Lewis acidity and an enhanced activity and selectivity. This is further explored by CD3CN spectroscopic sorption experiments. We have shown that by tuning the number of defects in UiO-66 using PSBA as the hemilabile linker, one can achieve highly defective and stable MOFs and easily control the Brønsted to Lewis acid ratio in the materials, and thus their catalytic activity and selectivity.

DOI

http://dx.doi.org/10.1021/jacs.9b13070

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jacs.9b13070.pdf

Defect engineering of UiO-66 using 4-sulfobenzoic acid

kevin — Wed, 01 Mar 2017 15:15:05 +0000

X. Feng, K. Hendrickx, G. Wang, K. Leus, V. Van Speybroeck, P. Van der Voort

ISBN/ISSN:

Poster

Conference / event / venue

Netherlands Catalysis and Chemistry Conference

Noordwijkerhout, The Netherlands

Monday, 6 March, 2017 to Wednesday, 8 March, 2017

Abstract (private)

abstract_submission-Xiao-final.pdf