4 results
Search Results
Now showing 1 - 4 of 4
- ItemAddressing the Reproducibility of Photocatalytic Carbon Dioxide Reduction(Weinheim : Wiley-VCH Verlag, 2019) Marx, Maximilian; Mele, Andrea; Spannenberg, Anke; Steinlechner, Christoph; Junge, Henrik; Schollhammer, Philippe; Beller, MatthiasReproducibility of photocatalytic reactions, especially when conducted on small scale for improved turnover numbers with in situ formed catalysts can prove challenging. Herein, we showcase the problematic reproducibility on the example of attractive photocatalytic CO2 reduction utilizing [FeFe] hydrogenase mimics. These Fe complexes, well-known for their application in proton reduction reactions, were combined with a heteroleptic Cu photosensitizer and produced CO/H2/HCO2H mixtures of variable constitution. However, the reactions indicated a poor reproducibility, even when conducted with well-defined complexes. Based on our experience, we make suggestions for scientists working in the field of photocatalysis on how to address and report the reproducibility of novel photocatalytic reaction protocols. In addition, we would like to highlight the importance of studying reproducibility of novel reaction protocols, especially in the fields of photocatalytic water splitting and CO2 reduction, where TONs are widely used as the comparable measure for catalytic activity. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemTetracarbonyl[4,4-dimethyl-2-(pyridin-2-yl)-2-oxazoline-κ2N,N′]molybdenum(0)(Chester : IUCr, 2019) Steinlechner, Christoph; Spannenberg, Anke; Junge, Henrik; Beller, MatthiasIn the title compound, [Mo(C10H12N2O)(CO)4], the molybdenum(0) center is surrounded by a bidentate diimine [4,4-dimethyl-2-(pyridin-2-yl)-2-oxazoline] and four carbonyl ligands in a distorted octahedral coordination geometry. The diimine ligand coordinates via the two nitrogen atoms.
- ItemEarth-abundant photocatalytic systems for the visible-light-driven reduction of CO2 to CO(Cambridge : RSC, 2017) Rosas-Hernández, Alonso; Steinlechner, Christoph; Junge, Henrik; Beller, MatthiasHerein, we report a highly selective photocatalytic system, based on an in situ copper photosensitizer and an iron catalyst, for the reduction of CO2 to CO. Turnover numbers (TON) up to 487 (5 h) with selectivities up to 99% and ΦCO = 13.3% were observed. Stern-Volmer analysis allowed us to establish a reductive quenching mechanism between the Cu PS and electron donor.
- ItemHydrogen production from formic acid catalyzed by a phosphine free manganese complex: Investigation and mechanistic insights(Cambridge : RSC, 2020) Léval, Alexander; Agapova, Anastasiya; Steinlechner, Christoph; Alberico, Elisabetta; Junge, Henrik; Beller, MatthiasFormic acid dehydrogenation (FAD) is considered as a promising process in the context of hydrogen storage. Its low toxicity, availability and convenient handling make FA attractive as a potential hydrogen carrier. To date, most promising catalysts have been based on noble metals, such as ruthenium and iridium. Efficient non-noble metal systems like iron were designed but manganese remains relatively unexplored for this transformation. In this work, we present a panel of phosphine free manganese catalysts which showed activity and stability in formic acid dehydrogenation. The most promising results were obtained with Mn(pyridine-imidazoline)(CO)3Br yielding >14 l of the H2/CO2 mixture and proved to be stable for more than 3 days. Additionally, this study provides insights into the mechanism of formic acid dehydrogenation. Kinetic experiments, Kinetic Isotopic Effect (KIE), in situ observations, NMR labeling experiments and pH monitoring allow us to propose a catalytic cycle for this transformation.