Prof. Jonathan De Roo: From the synthesis and surface chemistry of oxo clusters to the precise composition of Metal Organic Frameworks
Abstract : Zirconium and hafnium oxo clusters are building blocks for MOFs, 3D-printing and polymers composites. However, their synthesis is often a matter of trial and error, and new structures are hard to design retrosynthetically.
Here, we study the nonaqueous formation mechanism of the prototypical M6O4(OH)4(OOCR)12 (M = Zr or Hf) clusters. In the reaction of metal alkoxide with excess carboxylic acid, an asymmetric trinuclear complex is transiently formed. The reaction produces ester as by-product and we determine that precisely 1.33 equivalent of ester is required for every Zr atom to reach full yield of the oxo cluster. The esterification can be divided in a fast and slow process and the proposed mechanism is supported by kinetic modeling. We use our mechanistic insight to redesign oxo cluster synthesis with higher reaction rates, more economical precursors, more sustainable solvents and higher atom economy, all at room temperature at gram scale. Furthermore, we use precision hydrolysis to synthesize the elusive bimetallic Zr/Hf oxo clusters, and to expand rational oxo cluster synthesis to the group 5.
We leverage the atomically precise nature of oxo clusters to gain fundamental insight into the thermodynamics of ligand binding: carboxylates, phosphonates, dialkylphosphinates, and monosubstituted phosphinates. Dialkylphosphinic acids are too sterically hindered to yield complete ligand exchange. Monoalkyl or monoaryl phosphinic acids do replace carboxylates quantitatively. Phosphonic acids cause a partial structural reorganization of the metal oxo cluster into amorphous metal phosphonate, showing the challenge in preparing Zr phosphonate metal–organic frameworks.
Finally, we present a rigorous yet simple method for the accurate determination of a MOF's minimal formula. By combining quantitative nuclear magnetic resonance (NMR) and ultraviolet-visible (UV–vis) spectroscopy data with thermogravimetric analysis (TGA), the minimal formula of several MOFs – MOF-808(Zr), UiO-66(Zr), UiO-66(Ce), MOF-5(Zn), MIL-125(Ti), and MIL-100(Fe) – are constructed.
Bio : Jonathan De Roo was born in 1989 in Belgium. He studied chemistry at Ghent University and obtained his PhD on the surface chemistry of metal oxide nanocrystals in 2016 under supervision of Prof. Isabel Van Driessche, Prof. Zeger Hens and Prof. José Martins. During his PhD, he conducted a three month research stay in the lab of Prof. Maksym Kovalenko to study the surface of CsPbBr3 nanocrystals. He was a postdoctoral researcher at Columbia University (USA) for 2 years, working on crystallization mechanisms and custom-made ligands under supervision of Prof. Jonathan Owen. Before assuming his position at the University of Basel as assistant professor in September 2019, he spent one more year as post-doctoral researcher at Ghent University. He was promoted to Associate Professor with tenure in 2024.
Here, we study the nonaqueous formation mechanism of the prototypical M6O4(OH)4(OOCR)12 (M = Zr or Hf) clusters. In the reaction of metal alkoxide with excess carboxylic acid, an asymmetric trinuclear complex is transiently formed. The reaction produces ester as by-product and we determine that precisely 1.33 equivalent of ester is required for every Zr atom to reach full yield of the oxo cluster. The esterification can be divided in a fast and slow process and the proposed mechanism is supported by kinetic modeling. We use our mechanistic insight to redesign oxo cluster synthesis with higher reaction rates, more economical precursors, more sustainable solvents and higher atom economy, all at room temperature at gram scale. Furthermore, we use precision hydrolysis to synthesize the elusive bimetallic Zr/Hf oxo clusters, and to expand rational oxo cluster synthesis to the group 5.
We leverage the atomically precise nature of oxo clusters to gain fundamental insight into the thermodynamics of ligand binding: carboxylates, phosphonates, dialkylphosphinates, and monosubstituted phosphinates. Dialkylphosphinic acids are too sterically hindered to yield complete ligand exchange. Monoalkyl or monoaryl phosphinic acids do replace carboxylates quantitatively. Phosphonic acids cause a partial structural reorganization of the metal oxo cluster into amorphous metal phosphonate, showing the challenge in preparing Zr phosphonate metal–organic frameworks.
Finally, we present a rigorous yet simple method for the accurate determination of a MOF's minimal formula. By combining quantitative nuclear magnetic resonance (NMR) and ultraviolet-visible (UV–vis) spectroscopy data with thermogravimetric analysis (TGA), the minimal formula of several MOFs – MOF-808(Zr), UiO-66(Zr), UiO-66(Ce), MOF-5(Zn), MIL-125(Ti), and MIL-100(Fe) – are constructed.
Bio : Jonathan De Roo was born in 1989 in Belgium. He studied chemistry at Ghent University and obtained his PhD on the surface chemistry of metal oxide nanocrystals in 2016 under supervision of Prof. Isabel Van Driessche, Prof. Zeger Hens and Prof. José Martins. During his PhD, he conducted a three month research stay in the lab of Prof. Maksym Kovalenko to study the surface of CsPbBr3 nanocrystals. He was a postdoctoral researcher at Columbia University (USA) for 2 years, working on crystallization mechanisms and custom-made ligands under supervision of Prof. Jonathan Owen. Before assuming his position at the University of Basel as assistant professor in September 2019, he spent one more year as post-doctoral researcher at Ghent University. He was promoted to Associate Professor with tenure in 2024.
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- Institute of Chemical Sciences and Engineering
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- Wendy Queen
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