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Three CoII octaazacryptates, with different substituents on the aromatic rings (Br, NO2, CCH), were synthesised and characterised. These and the already published non‐substituted cryptate catalysed CO2 photoreduction to CO and CH4 under blue visible light at room temperature. Although CO was observed after short irradiation times and a large range of catalyst concentrations, CH4 was only observed after longer irradiation periods, such as 30 h, but with a small catalyst concentration (25 nm). Experiments with 13C labelled CO2 showed that CO is formed and reacts further when the reaction time is long. The CCH catalyst is deactivated faster than the others and the more efficient catalyst for CH4 production is the one with Br. This reactivity trend was explained by an energy decomposition analysis based on DFT calculations. [ABSTRACT FROM AUTHOR]

Keywords: carbon dioxide; cryptates; methane; photoreduction; visible light Carbon dioxide, cryptates, methane, photoreduction, visible light. [Extracted from the article]

Three Co II octaazacryptates, with different substituents on the aromatic rings (Br, NO 2 , CCH), were synthesised and characterised. These and the already published non-substituted cryptate catalysed CO 2 photoreduction to CO and CH 4 under blue visible light at room temperature. Although CO was observed after short irradiation times and a large range of catalyst concentrations, CH 4 was only observed after longer irradiation periods, such as 30 h, but with a small catalyst concentration (25 nm). Experiments with 13 C labelled CO 2 showed that CO is formed and reacts further when the reaction time is long. The CCH catalyst is deactivated faster than the others and the more efficient catalyst for CH 4 production is the one with Br. This reactivity trend was explained by an energy decomposition analysis based on DFT calculations., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)