Sustainable nitrophenol reduction using Ce-mof-808-supported bimetallic nanoparticles optimized by response surface methodology

This study presents the development and optimization of Ce-MOF-808 nanocrystals supported by metallic and bimetallic nanoparticles (Au, Ag, and Pd) for the efficient reduction of nitrophenol. Using a sol-immobilization method, we synthesized a series of catalysts, including Au/Ce-MOF-808, Au-Ag/Ce-MOF-808, and Au-Pd/Ce-MOF-808, and evaluated their catalytic efficacy of 4-nitrophenol (4-NP) reduction using NaBH₄ under mild conditions. Initially, effects of time (1-18 min), and catalyst dose (1-6 mg) on the reduction of nitrophenol were investigated through the one-factor-at-a-time experiment. Furthermore, the optimized experimental conditions (reduction time of 18 min, and catalyst dose 4.5 mg) were obtained using response surface methodology (RSM). X-ray photoelectron spectroscopy (XPS) and thermogravimetric assessment (TGA) further confirmed the robust interaction between metal nanoparticles and the Ce-MOF-808 framework, contributing to enhanced thermal stability and electron transfer capabilities. Among these, the Au-Ag/Ce-MOF-808 composite exhibited the highest catalytic activity, achieving a 98.3% conversion of 4-NP to 4-aminophenol (4-AP) within 18 min. Kinetic studies confirmed the superior catalytic performance of Au-Ag/Ce-MOF-808, with a rate constant (k_app) of 0.100 min⁻¹ and a reduced half-life of 9.6 min, highlighting the synergistic effects of Au and Ag nanoparticles in enhancing electron transfer and increasing active sites. The reusability tests demonstrated that Au-Ag/Ce-MOF-808 maintained high catalytic activity over five consecutive cycles, indicating its stability and suitability for continuous use. These findings underscore the potential of metal-modified Ce-MOF-808 catalysts for sustainable environmental applications, offering high efficiency, durability, and the ability to operate under mild conditions.