Cellulose Film-Integrated Gold Nanoparticles Synthesized in Ionic Liquids for Heterogeneous Catalysis

Abstract

Taking advantage of the unique structural directionality of ionic liquids, we successfully synthesized highly concentrated gold nanoparticles (AuNPs) in 1-octyl-3-methylimidazolium chloride (OMImCl) using tetrabutylammonium borohydride (TBABH₄) as the reducing agent. It is a distinctly different approach, avoiding additional capping agents and producing spherical AuNPs of approximately 10 nm diameter at varying concentrations. To prevent nanoparticle aggregation during catalytic reactions and enhance catalyst reusability, these AuNPs were immobilized in cellulose films. The film fabrication involved blending each AuNP dispersion with microcrystalline cellulose dissolved in 1-butyl-3-methylimidazolium chloride (BMImCl) and further water regeneration. Therefore, these films, containing up to 1.30% AuNPs, efficiently reduced 4-nitrophenol (4-NP) using sodium borohydride. Remarkably, the catalysts remained effective through five cycles without noticeable degradation. Compared to other methods, our catalysts displayed a higher turnover frequency (TOF), especially in films with lower gold content, due to their smaller particle size and uniform distribution. Our approach, avoiding the need for complex recovery processes typical of powder-based catalysts, offers an environmentally friendly, efficient, and reusable solution, emphasizing its potential for robust catalytic applications.