Transforming Biowaste into Nanocatalysts: Polyphenol-Engineered Core–Shell Silica Nanoparticles for Multifaceted Application

Abstract

The integration of cost-effective, nontoxic, and environmentally friendly core−shell nanomaterials using green waste is crucial for diverse industrial applications. Traditional metal-based nanoparticles and nanocomposites used in Beckmann rearrangement and dye degradation pose significant energy, environmental, and health challenges. In this work, we introduce nanoscale core−shell Polyphenol-functionalized silica nanoparticles (SP NPs) as a green nanocatalyst for Beckmann rearrangement and dye degradation, adhering to green chemistry principles. The SP NPs are prepared through a two-step process: creating an ester linkage between polyphenols and silica with a carboxyl terminal followed by hydrogen bonding of silica over the polyphenol surface. The resulting core−shell structure, with a 48 nm silica-polyphenol core and a 10 nm silica shell, was confirmed by HR-TEM and dynamic light scattering measurements. These stable nanoparticles serve as an efficient nanocatalyst for the room temperature conversion of oxime to amide with a simple purification strategy, achieving a conversion efficiency of 97.2% without acids or solvents, surpassing conventional methods. The environmental and economic viability of this material in the Beckmann rearrangement is validated by an Ecoscale score of 90.61 and favorable green metrics such as an E-factor of 0.0288 and reaction mass efficiency of 97.2%. Additionally, the hydrogen radical generation capability of SP NPs enables the reduction of industrial organic pollutants such as dyes without external light sources, achieving over 99% dye degradation. The synergistic behavior of the core−shell morphology provides an eco-friendly, reusable catalyst, offering a practical and sustainable solution to industrial and environmental challenges associated with the Beckmann rearrangement and dye degradation.