F. Muniz-Miranda

Elucidation of the pre-nucleation phase directing metal-organic framework formation

M. Filez, C. Caratelli, M. Rivera-Torrente, F. Muniz-Miranda, M. Hoek, M. Altelaar, A.J.R. Heck, V. Van Speybroeck, B.M. Weckhuysen
Cell Reports Physical Science
2, 12, 100680


Metal-organic framework (MOF) crystallization is governed by molecular assembly processes in the pre-nucleation stage. Yet, unravelling these pre-nucleation pathways and rationalizing their impact on crystal formation poses a great challenge since probing molecular-scale assemblies and macroscopic particles simultaneously is very complex. Herein, we present a multimodal, integrated approach to monitor MOF nucleation across multiple length scales by combining in situ optical spectroscopy, mass spectrometry, and molecular simulations. This approach allows tracing initial metal-organic complexes in solution and their assembly into oligomeric nuclei and simultaneously probing particle formation. During Co-ZIF-67 nucleation, a metal-organic pool forms with a variety of complexes caused by ligand exchange and symmetry reduction reactions. We discriminate complexes capable of initiating nucleation from growth species required for oligomerization into frameworks. Co4-nuclei are observed, which grow into particles following autocatalytic kinetics. The geometric and compositional variability of metal-organic pool species clarifies long-debated amorphous zeolitic imidazolate framework (ZIF)-particle nucleation and non-classic pathways of MOF crystallization.



Elucidating the promotional effect of a covalent triazine framework in aerobic oxidation

S. Abednatanzi, P. Gohari Derakhshandeh, P. Tack, F. Muniz-Miranda, Y-Y Liu, J. Everaert, M. Meledina, F. Vanden Bussche, L. Vincze, C. Stevens, V. Van Speybroeck, H. Vrielinck, F. Callens, K. Leus, P. Van der Voort
Applied Catalysis B: Environmental
269, 118769

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


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

Optical Properties of Isolated and Covalent Organic Framework-Embedded Ruthenium Complexes

F. Muniz-Miranda, L. De Bruecker, A. De Vos, F. Vanden Bussche, C.V. Stevens, P. Van der Voort, K. Lejaeghere, V. Van Speybroeck
Journal of Physical Chemistry A
123 (32), 6854-6867


Heterogenization of RuL3 complexes on a support with proper anchor points provides a route toward design of green catalysts. In this paper, Ru(II) polypyridyl complexes are investigated with the aim to unravel the influence on the photocatalytic properties of varying nitrogen content in the ligands and of embedding the complex in a triazine-based covalent organic framework. To provide fundamental insight into the electronic mechanisms underlying this behavior, a computational study is performed. Both the ground and excited state properties of isolated and anchored ruthenium complexes are theoretically investigated by means of density functional theory and time-dependent density functional theory. Varying the ligands among 2,2′-bipyridine, 2,2′-bipyrimidine, and 2,2′-bipyrazine allows us to tune to a certain extent the optical gaps and the metal to ligand charge transfer excitations. Heterogenization of the complex within a CTF support has a significant effect on the nature and energy of the electronic transitions. The allowed transitions are significantly red-shifted toward the near IR region and involve transitions from states localized on the CTF toward ligands attached to the ruthenium. The study shows how variations in ligands and anchoring on proper supports allows us to increase the range of wavelengths that may be exploited for photocatalysis.

Gold Open Access

Electronic properties of heterogenized Ru(II) polypyridyl photoredox complexes on covalent triazine frameworks

A. De Vos, K. Lejaeghere, F. Muniz-Miranda, C. Stevens, P. Van der Voort, V. Van Speybroeck
Journal of Materials Chemistry A
7, 8433-8442


Ru(II) polypyridyl complexes have been successful for a wide range of photoredox applications thanks to their efficient light-induced metal-to-ligand charge transfer. Using the computational framework of density-functional theory, we report how these complexes can be anchored onto covalent triazine frameworks while maintaining their favorable electronic properties. We moreover show that variation of the nitrogen content of the framework linkers or complex ligands endows the heterogenized catalyst with a unique versatility, spanning a wide range of absorption characteristics and redox potentials. By judiciously choosing the catalyst building blocks, it is even possible to selectively guide the charge transfer toward either the scaffold or the accessible pore sites. Rational design of sustainable and efficient photocatalysts thus comes within reach.

Immobilization of Ir(I) complex on Covalent Triazine Frameworks for C-H Borylation Reactions: A Combined Experimental and Computational Study

N. Tahir, F. Muniz-Miranda, J. Everaert, P. Tack, T.S.A Heugebaert, K. Leus, L. Vincze, C. Stevens, V. Van Speybroeck, P. Van der Voort
Journal of Catalysis
371, 135-143


Metal-modified covalent triazine frameworks (CTFs) have attracted considerable attention in heterogeneous catalysis due to their strong nitrogen-metal interactions exhibiting superior activity, stability and hence recyclability. Herein, we report on a post-metalation of a bipyridine-based CTFs with an Ir(I) complex for CH borylation of aromatic compounds. Physical characterization of the Ir(I)-based bipyCTF catalyst in combination with density functional theory (DFT) calculations exhibit a high stabilization energy of the Ir-bipy moiety in the frameworks in the presence of B2Pin2. By using B2Pin2 as a boron source, Ir(I)@bipyCTF efficiently catalyzed the CH borylation of various aromatic compounds with excellent activity and good recyclability. In addition, XAS analysis of the Ir(I)@bipyCTF gave clear evidence for the coordination environment of the Ir.

First-principles insight into Heterogeneous Photocatalysis at photoactive Ru-complexes on Covalent Triazine Frameworks


Conference / event / venue 

6th International Conference on Metal-Organic Frameworks
Auckland, New Zealand
Sunday, 9 December, 2018 to Thursday, 13 December, 2018


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