Enhancing Photoredox Catalysis in Aqueous Environments: Ruthenium Aqua Complex Derivatization of Graphene Oxide and Graphite Rods for Efficient Visible-Light-Driven Hybrid Catalysts

Syrine Affès; Akrivi-Maria Stamatelou; Xavier Fontrodona; Ahlem Kabadou; Clara Viñas; Francesc Teixidor; Isabel Romero

doi:10.1021/acsami.3c13156

Enhancing Photoredox Catalysis in Aqueous Environments: Ruthenium Aqua Complex Derivatization of Graphene Oxide and Graphite Rods for Efficient Visible-Light-Driven Hybrid Catalysts

ACS Appl Mater Interfaces. 2024 Jan 10;16(1):507-519. doi: 10.1021/acsami.3c13156. Epub 2023 Dec 19.

Authors

Syrine Affès^{1

2}, Akrivi-Maria Stamatelou¹, Xavier Fontrodona¹, Ahlem Kabadou², Clara Viñas³, Francesc Teixidor³, Isabel Romero¹

Affiliations

¹ Departament de Química and Serveis Tècnics de Recerca, Universitat de Girona, C/M. Aurèlia Campmany, 69, Girona E-17003, Spain.
² Laboratoire des Sciences des Matériaux et d'Environnement, Faculté des Sciences, Université de Sfax, Sfax 3000, Tunisie.
³ Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, Campus UAB, Bellaterra E-08193, Spain.

Abstract

A ruthenium aqua photoredox catalyst has been successfully heterogeneneized on graphene oxide (GO@trans-fac-3) and graphite rods (GR@trans-fac-3) for the first time and have proven to be sustainable and easily reusable systems for the photooxidation of alcohols in water, in mild and green conditions. We report here the synthesis and total characterization of two Ru(II)-polypyridyl complexes, the chlorido trans-fac-[RuCl(bpea-pyrene)(bpy)](PF₆) (trans-fac-2) and the aqua trans-fac-[Ru(bpea-pyrene)(bpy)OH₂](PF₆)₂ (trans-fac-3), both containing the N-tridentate, 1-[bis(pyridine-2-ylmethyl)amino]methylpyrene (bpea-pyrene), and 2,2'-bipyridine (bpy) ligands. In both complexes, only a single isomer, the trans-fac, has been detected in solution and in the solid state. The aqua complex trans-fac-3 displays bielectronic redox processes in water, assigned to the Ru(IV/II) couple. The trans-fac-3 complex has been heterogenized on different types of supports, (i) on graphene oxide (GO) through π-stacking interactions between the pyrene group of the bpea-pyrene ligand and the GO and (ii) both on glassy carbon electrodes (GC) and on graphite rods (GR) through oxidative electropolymerization of the pyrene group, which yield stable heterogeneous photoredox catalysts. GO@trans-fac-3- and GR/poly trans-fac-3-modified electrodes were fully characterized by spectroscopic and electrochemical methods. Trans-fac-3 and GO@trans-fac-3 photocatalysts (without a photosensitizer) showed good catalytic efficiency in the photooxidation of alcohols in water under mild conditions and using visible light. Both photocatalysts display high selectivity values (>99%) even for primary alcohols in accordance with the presence of two-electron transfer processes (2e^-/2H⁺). GO@trans-fac-3 keeps intact its homogeneous catalytic properties but shows an enhancement in yields. GO@trans-fac-3 can be easily recycled by filtration and reused for up to five runs without any significant loss of catalytic activity. Graphite rods (GR@trans-fac-3) were also evaluated as heterogeneous photoredox catalysts showing high turnover numbers (TON) and selectivity values.

Keywords: aqueous medium; graphene oxide; graphite; heterogeneous catalysis; photoredox oxidation; ruthenium.