Optimizing noble metals exploitation in water oxidation catalysis by their incorporation in layered double hydroxides

Zaccaria, Francesco; Fagiolari, Lucia; Macchioni, Alceo

doi:10.1016/j.ica.2020.120161

Cited by 9 publications

(6 citation statements)

References 95 publications

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“…In the case of oxidation reactions, the quest for selective processes poses an everyday challenge to both academia and industry [1][2][3][4][5][6][7]. To achieve the goal of developing such processes, catalysts have been produced to address the need for operating chemical transformations in an efficient and selective way.…”

Section: Introductionmentioning

confidence: 99%

Substrate–Solvent Crosstalk—Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

et al. 2021

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In this work, we explored how solvents can affect olefin oxidation reactions catalyzed by MCM-bpy-Mo catalysts and whether their control can be made with those players. The results of this study demonstrated that polar and apolar aprotic solvents modulated the reactions in different ways. Experimental data showed that acetonitrile (aprotic polar) could largely hinder the reaction rate, whereas toluene (aprotic apolar) did not. In both cases, product selectivity at isoconversion was not affected. Further insights were obtained by means of neutron diffraction experiments, which confirmed the kinetic data and allowed for the proposal of a model based on substrate–solvent crosstalk by means of hydrogen bonding. In addition, the model was also validated in the ring-opening reaction (overoxidation) of styrene oxide to benzaldehyde, which progressed when toluene was the solvent (reaching 31% styrene oxide conversion) but was strongly hindered when acetonitrile was used instead (reaching only 7% conversion) due to the establishment of H-bonds in the latter. Although this model was confirmed and validated for olefin oxidation reactions, it can be envisaged that it may also be applied to other catalytic reaction systems where reaction control is critical, thereby widening its use.

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Section: Introductionmentioning

confidence: 99%

Substrate–Solvent Crosstalk—Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

et al. 2021

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“…In the vast realm of known WO catalysts (WOCs), significant progress has been recently made in the exploitation of base metals (e.g., Fe, Co, and Ni); − yet, the performance of noble metal systems (e.g., Ru and Ir) − still appears more promising, especially in terms of durability. This is why many research groups have engaged in the development of molecular, − heterogenized, ,− and heterogeneous − WOCs following a “noble-metal atom economy” approach . Despite the noticeable progress over the last decade, however, catalytic performance is still far from that desirable for commercial application.…”

Section: Introductionmentioning

confidence: 99%

Substituent Effects on the Activity of Cp*Ir(pyridine-carboxylate) Water Oxidation Catalysts: Which Ligand Fragments Remain Coordinated to the Active Ir Centers?

et al. 2021

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Identifying structure–property correlations for molecular water oxidation catalysts (WOCs) is strongly hampered by the complexity of the water oxidation (WO) reaction mechanism and catalyst in situ modifications. Here, the substitution effects for [Cp*Ir(X-pic)NO3] WOCs (pic = κ2-pyridine-2-carboxylate complexes) have been systematically explored by synthesizing several complexes differing for the nature of the X substituent on the pyridine-carboxylate ligand and testing them in WO driven by NaIO4. The activity data were correlated with the σ-Hammett parameter of the various substituents, which was proven to effectively reproduce the trends in electron donor properties of the ligands. The measured TOFmax values were found to roughly increase with the σ-Hammett parameter (i.e., with decreasing electron density at the metal center), reaching plateaux at activity values comparable to that of the simpler [Cp*Ir(H2O)3](NO3)2 catalyst. This trend has been typically observed for WOCs following a water nucleophilic attack mechanism. However, nuclear magnetic resonance studies on the reaction between [Cp*Ir(X-pic)NO3] and NaIO4 suggest that the activity is actually determined by the ease of pyridine-carboxylate ligand loss, likely being a necessary step toward precatalyst activation. This indicates that the same active species is generated from all [Cp*Ir(X-pic)NO3] starting complexes, albeit at different rates and/or in different amounts. A somewhat clear picture therefore appears to emerge, partially in contradiction with some of the hypotheses previously proposed: the active species should contain some degradation fragments of the Cp* (based on previous literature studies) and no X-pic derived ligands (based on the results reported in this work).

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“…In the case of oxidation reactions, the quest for selective processes poses an everyday challenge to both academy and industry [1][2][3][4][5][6][7]. To achieve that goal catalysts have been developed to address the need of operating chemical transformations in an efficient and selective way.…”

Section: Introductionmentioning

confidence: 99%

Substrate-Solvent Crosstalk – Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

Sales¹,

Callear²,

Vaz³

et al. 2021

Preprint

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In this work we explored how solvents can affect olefin oxidation reactions catalyzed by MCM-bpy-Mo catalysts and whether their control can be made with those players. The results of this study evidenced that polar and apolar aprotic solvents modulated the reactions in different ways. Experimental data showed that acetonitrile (aprotic polar) could hinder largely the reaction rate whereas toluene (aprotic apolar) did not. In both cases product selectivity at isoconversion was not affected. Further insights were obtained by means of neutron diffraction experiments, which confirmed the kinetic data allowing to propose a model based on substrate-solvent crosstalk by means of hydrogen bonding. In addition, the model was also validated in the ring-opening reaction (overoxidation) of styrene oxide towards benzaldehyde, which progressed when toluene was the solvent (reaching 31% styrene oxide conversion) but was strongly hindered when acetonitrile was used instead (reaching only 7% conversion), due to the establishment of H-bonds in the latter. Although this model was confirmed and validated for olefin oxidation reactions, it can be envisaged that it may also be applied to other catalytic reaction systems where reaction control is critical, while widening its use.

show abstract

Optimizing noble metals exploitation in water oxidation catalysis by their incorporation in layered double hydroxides

Cited by 9 publications

References 95 publications

Substrate–Solvent Crosstalk—Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

Substrate–Solvent Crosstalk—Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

Substituent Effects on the Activity of Cp*Ir(pyridine-carboxylate) Water Oxidation Catalysts: Which Ligand Fragments Remain Coordinated to the Active Ir Centers?

Substrate-Solvent Crosstalk – Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

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