Spaced Double Hydrogen Bonding in an Imidazole Poly Ionic Liquid Composite for Highly Efficient and Selective Photocatalytic Air Reductive H₂O₂ Synthesis

Abstract

Photocatalytic oxygen reductive H₂O₂ production is a promising approach to alternative industrial anthraquinone processes while suffering from the requirement of pure O₂ feedstock for practical application. Herein, we report a spaced double hydrogen bond (IC-H-bond) through multi-component Radziszewski reaction in an imidazole poly-ionic-liquid composite (SI-PIL-TiO₂) and levofloxacin hydrochloride (LEV) electron donor for highly efficient and selective photocatalytic air reductive H₂O₂ production. It is found that the IC-H-bond formed by spaced imino (-NH-) group of SI-PIL-TiO₂ and carbonyl (-C=O) group of LEV can switch the imidazole active sites characteristic from a covered state to a fully exposed one to shield the strong adsorption of electron donor and N₂ in the air, and propel an intenser positive potential and more efficient orbitals binding patterns of SI-PIL-TiO₂ surface to establish competitive active sites for selectivity O₂ chemisorption. Moreover, the high electron enrichment of imidazole as an active site for the 2e^- oxygen reduction ensures the rapid reduction of O₂. Therefore, the IC-H-bond enables a total O₂ utilization and conversion efficiency of 94.8 % from direct photocatalytic air reduction, achieving a H₂O₂ production rate of 1518 μmol/g/h that is 16 and 23 times compared to poly-ionic-liquid composite without spaced imino groups (PIL-TiO₂) and TiO₂, respectively.