Supporting non-noble metal composite organosilica monolithic foam for efficiently catalytic degradation of aromatic compounds

Abstract

The porous monolithic materials supporting non-noble metal nanoparticles that acted as catalysts have recently gained increasing attention due to their robust activity and regenerative ability, resulting in simple chemical progress. It is crucial for the catalytic performance that the monolithic supporters have a hierarchically porous structure while the non-noble metal nanoparticles show a good control of their dimensions and oxidation states. Herein this work reports the composite organosilica monolithic (OSM) foams containing non-noble metal like Cu-, Co-, or Ni-based nanoparticles. As-prepared the supporting non-noble metal nanoparticles organosilica monolithic foams could act as monolithic catalyst, showing the efficiently catalytic performance for the degradation of aromatic compounds. These monolithic catalysts were prepared via amino-functionalization of organosilica monolith with ethylenic groups, followed by supporting non-noble metal nanoparticles through a simple reduction process. The monolithic catalyst involved Cu-based nanoparticles (Cu/OSM) were obtained via reduction of Cu²⁺ using a mixture of NaBH₄ with and without the aid of polyvinylpyrrolidone K 90 (PVP), as denoted by Cu/OSM-N and Cu/OSM-P, respectively. It was demonstrated that the addition of PVP into the system caused the higher Cu content, the better distribution of the smaller Cu-based nanoparticles and a richer Cu(0) nanoparticles. Furthermore Cu/OSM-P exhibited high stability and durable activity, with approximately 95% conversion within 14 successive cycles, for the catalytic reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) with excess NaBH₄ in an aqueous solution. This catalyst also showed a remarkable catalytic performance for the degradation of other organic aromatic dyes like methylene blue (MB), methyl orange (MO), rhodamine B (RhB) and even their mixture. In addition, Co/OSM-P and Ni/OSM-P fabricated with the same method also showed high catalytic performance for reduction of 4-NP. We believe that the strategy developed in this work is very useful for the simple, low-cost, and environmentally friendly preparation of porous composite monolithic catalysts containing non-noble metal nanoparticles.