First Phenol Carboxylation with CO₂ on Carbon Nanostructured C@Fe-Al₂O₃ Hybrids in Aqueous Media under Mild Conditions

Novel hybrid materials with integrated catalytic properties and hydrophobic response, C@Fe-Al₂O₃ hybrid samples, were presented and tested as catalysts for phenol reaction in aqueous solutions at atmospheric pressure and mild temperature conditions, using CO₂ as a feedstock. A series of carbon-coated γ-alumina pellets (C@Fe-Al₂O₃) were synthesized and characterized by TGA, Brunauer-Emmett-Teller (BET) method, Raman spectroscopy, SEM, TEM, and XPS in order to get comprehensive knowledge of their properties at the nanoscale and relate them with their catalytic behavior. The results obtained correlated their catalytic activities with their carbon surface compositions. The application of these materials as active catalysts in the Kolbe-Schmitt reaction for CO₂ conversion in aqueous media was proposed as an alternative reaction for the valorization of exhausts industrial effluents. In these early tests, the highest conversion of phenol was observed for the hybrid samples with the highest graphitic characteristic and the most hydrophobic behavior. Carboxylation products such as benzoic acid, p-hydroxybenzoic acid, and salicylic acid, have been identified under these experimental conditions.