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A series of metal-free imidazole-benzimidazole catalysts (ImBenz-H, ImBenz-NO 2 , ImBenz-OCH 3 ) for oxygen reduction reaction (ORR) were prepared. We demonstrate that the electrocatalytic O 2 reduction by ImBenz-NO 2 with the electron-withdrawing group showed high selectivity toward H 2 O with the number of electrons transferred (n=3.7) in a neutral aqueous solution. The highest ORR selectivity toward H 2 O 2 was achieved using ImBenz-H (n=2.4) in an alkaline solution. Electrochemical studies of reaction kinetics disclosed that the highest turnover frequencies were obtained from ImBenz-H in both neutral and alkaline aqueous solutions. The results prove that the ORR selectivity is tunable by modulating the substituent of the ImBenz catalysts. Furthermore, DFT calculations suggested that the ORR mechanism of ImBenz-H involves the electron transfer from imidazole-benzimidazole to O 2 resulting in the formation of H 2 O 2 which supports the redox active properties of the catalysts ImBenz., (© 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

Ensuring continuous and sustainable lithium supply requires the development of highly efficient separation processes such as LLE (liquid-liquid extraction) for both primary sources and certain waste streams. In this work, 4-phosphoryl pyrazolones are used in an efficient pH-controlled stepwise separation of Li + from Ca 2+ , Mg 2+ , Na + and K + . The factors affecting LLE process, such as the substitution pattern of the extractant, diluent/water distribution, co-ligand, pH, and speciation of the metal complexes involved, were systematically investigated. The maximum extraction efficiency of Li + at pH 6.0 was 94 % when Mg 2+ and Ca 2+ were previously separated at pH<5.0, proving that the separation of these ions is possible by simply modulating the pH of the aqueous phase. Our study points a way to separation of lithium from acid brine or from spent lithium ion battery leaching solutions, which supports the future supply of lithium in a more environmentally friendly and sustainable manner., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)