Center for Molecular Modeling - D. Poelman

Development of porous organic polymers as metal free photocatalysts for the aromatization of N-heterocycles

leen — Thu, 07 Dec 2023 07:12:22 +0000

M. Debruyne, N. Raeymackers, H. Vrielinck, S. Radhakrishnan, E. Breynaert, M. Delaey, A. Laemont, K. Leus, J. Everaert, H. Rijckaert, D. Poelman, R. Morent, N. De Geyter, P. Van der Voort, V. Van Speybroeck, C. Stevens, T.S.A Heugebaert

ChemCatChem

2024

Abstract

Porous organic polymers (POPs), and especially covalent triazine frameworks (CTFs), are being developed as the next generation of metal-free heterogeneous photocatalysts. However, many of the current synthetic routes to obtain these photoactive POPs require expensive monomers and rely on precious metal catalysts, thus hindering their widespread implementation. In this work, a range of POPs was synthesized from simple unfunctionalized aromatic building blocks, through Lewis acidcatalyzed polymerization. The obtained materials were applied, for the first time, as heterogeneous photocatalysts for the aromatization of N-heterocycles. With the use of the most active material, denoted as CTF-Pyr, which consists of photoactive pyrene and triazine moieties, a wide range of pyridines, dihydroquinoline-5-ones, tetrahydroacridine-1,8-diones and pyrazoles were obtained in excellent yields (70-99%). Moreover, these reactions were carried out under very mild conditions using air and at room temperature, highlighting the potential of these materials as catalysts for green transformations.

DOI

https://doi.org/10.1002/cctc.202301205

Private attachment

Development of porous organic polymers as metal free photocatalysts for the aromatization.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

Exploring lanthanide doping in UiO-66: a combined experimental and computational study of the electronic structure

kurt — Fri, 23 Feb 2018 19:50:21 +0000

K. Hendrickx, J.J. Joos, A. De Vos, D. Poelman, P. F. Smet, V. Van Speybroeck, P. Van der Voort, K. Lejaeghere

Inorganic Chemistry

57, 5463-5474

2018

DOI

http://dx.doi.org/10.1021/acs.inorgchem.8b00425

Private attachment

Hendrickx_2018_InorgChem_lanthanide-UiO-electronic.pdf

Manuscript.pdf

Charge transfer induced energy storage in CaZnOS:Mn - insight from experimental and computational spectroscopy

kurt — Sat, 24 Sep 2016 09:46:09 +0000

J.J. Joos, K. Lejaeghere, K. Korthout, A. Feng, D. Poelman, P. F. Smet

Physical Chemistry Chemical Physics (PCCP)

19 (13), 9075-9085

2017

Abstract

CaZnOS:Mn2+ is a rare-earth-free luminescent compound with an orange broadband emission at 612 nm, featuring pressure sensing capabilities, often explained by defect levels where energy can be stored. Despite recent efforts from experimental and theoretical points of view, the underlying luminescence mechanisms in this phosphor still lack a profound understanding. By the evaluation of thermoluminescence as a function of the charging wavelength, we probe the defect levels allowing energy storage. Multiple trap depths and trapping routes are found, suggesting predominantly local trapping close to Mn2+ impurities. We demonstrate that this phosphor shows mechanoluminescence which is unexpectedly stable at high temperature (up to 200 °C), allowing pressure sensing in a wide temperature range. Next, we correlate the spectroscopic results with a theoretical study of the electronic structure and stability of the Mn defects in CaZnOS. DFT calculations at the PBE+U level indicate that Mn impurities are incorporated on the Zn site in a divalent charge state, which is confirmed by X-ray absorption spectroscopy (XAS). Ligand-to-metal charge transfer (LMCT) is predicted from the location of the Mn impurity levels, obtained from the calculated defect formation energies. This LMCT proves to be a very efficient pathway for energy storage. The excited state landscape of the Mn2+ 3d5 electron configuration is assessed through the spin-correlated crystal field and a good correspondence with the emission and excitation spectra is found. In conclusion, studying phosphors at both a single-particle level (i.e. via calculation of defect formation energies) and a many-particle level (i.e. by accurately localizing the excited states) is necessary to obtain a complete picture of luminescent defects, as demonstrated in the case of CaZnOS:Mn2+.

Open Access version available at UGent repository

Gold Open Access

DOI

http://dx.doi.org/10.1039/C7CP00285H

Private attachment

c7cp00285h.pdf

Au@UiO-66: a base free oxidation catalyst

michel — Wed, 12 Nov 2014 16:36:37 +0000

K. Leus, P. Concepcion, M. Vandichel, M. Meledina, A. Grirrane, D. Esquivel, S. Turner, D. Poelman, M. Waroquier, V. Van Speybroeck, G. Van Tendeloo, H. Garcia, P. Van der Voort

RSC Advances

5 (29), 22334–22342

2015

Abstract

We present the in situ synthesis of Au nanoparticles within the Zr based Metal Organic Framework, UiO-66. The resulting Au@UiO-66 materials were characterized by means of N2 sorption, XRPD, UV-Vis, XRF, XPS and TEM analysis. The Au nanoparticles (NP) are homogeneously distributed along the UiO-66 host matrix when using NaBH4 or H2 as reducing agents. The Au@UiO-66 materials were evaluated as catalysts in the oxidation of benzyl alcohol and benzyl amine employing O2 as oxidant. The Au@MOF materials exhibit a very high selectivity towards the ketone (up to 100 %). Regenerability and stability tests demonstrate that the Au@UiO-66 catalyst can be recycled with a negligible loss of Au species and no loss of crystallinity. In situ IR measurements of UiO-66 and Au@UiO-66-NaBH4, before and after treatment with alcohol, showed an increase in IR bands that can be assigned to a combination of physisorbed and chemisorbed alcohol species. This was confirmed by velocity power spectra obtained from the molecular dynamics simulations. Active peroxo and oxo species on Au could be visualized with Raman analysis.

Open Access version available at UGent repository

DOI

http://dx.doi.org/10.1039/C4RA16800C

Private attachment

15_RSC_Adv_5_22334_Leus.pdf

Bipyridine-Based Nanosized Metal–Organic Framework with Tunable Luminescence by a Postmodification with Eu(III): An Experimental and Theoretical Study

michel — Wed, 06 Feb 2013 12:44:57 +0000

Y-Y Liu, R. Decadt, T. Bogaerts, K. Hemelsoet, A.M. Kaczmarek, D. Poelman, M. Waroquier, V. Van Speybroeck, R. Van Deun, P. Van der Voort

Journal of Physical Chemistry C

117 (21), 11302–11310

2013

Abstract

A gallium 2,2′-bipyridine-5,5′-dicarboxylate metal-organic framework, Ga(OH)(bpydc), denoted as COMOC-4 (COMOC = Center for Ordered Materials, Organometallics and Catalysis, Ghent University) has been synthesized via solvothermal synthesis procedure. The structure has the topology of an aluminum 2,2′-bipyridine-5,5′-dicarboxylate, the so-called MOF-253. TEM and SEM micrographs show the COMOC-4 crystals are formed in nanoplates with uniform size of 30-50 nm. The UV-Vis spectra of COMOC-4 in methanol solution show maximal electronic absorption at 307 nm. This results from linker to linker transitions as elucidated by time-dependent density functional theory simulations on the linker and COMOC-4 cluster models. When excited at 400 nm, COMOC-4 displays an emission band centered at 542 nm. Upon immersion in different solvents, the emission band for the framework is shifted in the range of 525~548 nm, depending on the solvent. After incorporating Eu3+ cations, the emission band of the framework is shifted to even shorter wavelengths (505 nm). By varying the excitation wavelengths from 250 to 400 nm, we can fine-tune the emission from red to yellowish green in the CIE diagram. The luminescence behavior of Eu3+ cations is well preserved and the solid state luminescence lifetimes of λ1 = 45 µs (35.4 %) and λ2 = 162 µs (64.6 %) are observed.

DOI

http://dx.doi.org/10.1021/jp402154q

Private attachment

13_jphyschemC_117_11302_Liu.pdf

Au@UiO-66 : a base free oxidation catalyst

samuel — Thu, 06 Feb 2020 09:59:43 +0000

K. Leus, P. Concepcion, M. Meledina, M. Vandichel, A. Girrane, D. Esquivel, S. Turner, D. Poelman, M. Waroquier, V. Van Speybroeck

ISBN/ISSN:

Talk

Conference / event / venue

16th Netherlands' Catalysis and Chemistry Conference (NCCC-XVI)

Noordwijkerhout, The Netherlands

Monday, 2 March, 2015 to Wednesday, 4 March, 2015

Mn impurities in CaZnOS: insight from luminescence spectroscopy and density functional theory

kurt — Fri, 26 Jan 2018 07:53:23 +0000

J.J. Joos, K. Lejaeghere, K. Korthout, A. Feng, D. Poelman, P.F. Smet

ISBN/ISSN:

Talk

Conference / event / venue

Workshop on Charge Trapping Defects in Semiconductors and Insulators

York, UK

Monday, 20 March, 2017 to Tuesday, 21 March, 2017

Au@UiO-66: a base free oxidation catalyst (vol 5, pg 22334, 2015)

wim — Tue, 28 Apr 2015 07:41:40 +0000

K. Leus, P. Concepcion, M. Meledina, A. Grirrane, D. Esquivel, S. Turner, D. Poelman, M. Waroquier, V. Van Speybroeck, G. Van Tendeloo, H. Garcia, P. Van der Voort

RSC Adv.

2015

Correction

Au@UiO-66: a base free oxidation catalyst

mat — Wed, 05 Nov 2014 10:02:06 +0000

K. Leus, P. Concepcion, M. Meledina, M. Vandichel, A. Grirrane, S. Turner, D. Poelman, M. Waroquier, V. Van Speybroeck, G. Van Tendeloo, H. Garcia, P. Van der Voort

ISBN/ISSN:

Talk

Conference / event / venue

DZA2014

Ghent, Belgium

Tuesday, 7 October, 2014 to Friday, 7 November, 2014