Photocatalytic CO₂ Reduction Using Ni(II) and Co(II) Cryptates: Influence of Ionic Liquids and Light Sources

Abstract The photoreduction of CO 2 offers a sustainable route for mitigating atmospheric CO 2 levels while producing added value chemicals. This study explores the use of Ni(II) and Co(II) octaazacryptates complexes as catalysts in the presence of different ionic liquids under blue LED and solar light conditions. By employing a systematic approach to vary ionic liquid concentrations and light sources, the catalytic performance was assessed in terms of CO production, H 2 production, CO selectivity, turnover number, and photoreaction quantum yield. The findings reveal that ionic liquid 1‐ethyl‐4‐picolinium triflate significantly enhances CO 2 reduction efficiency under solar light, with the highest CO yield of 15.75 µmol and CO turnover number of 1575 observed when using 2%w/w of the ionic liquid. Conversely, higher ionic liquid concentrations improved selectivity at the expense of CO production. The experiments conducted under sunlight demonstrated a compromise between selectivity and turnover, with the highest CO turnover number achieved for ionic liquid experiments, but greater selectivity in the absence of ionic liquid. These results underscore the importance of ionic liquid concentration in modulating catalytic performance, while also highlighting the potential of direct sunlight as a sustainable and powerful energy source for scalable, eco‐friendly CO 2 photoreduction systems.