Copper upcycling by hierarchical porous silica spheres functionalized with branched polyethylenimine: Antimicrobial and catalytic applications

Abstract

The increment of environmental pollution from heavy metals released by industrial or urban sources drives the development of new smart adsorbents. In particular, copper pollution is a rising concern due to its presence in industrial streams and electronic wastes. Mesoporous silica is a useful adsorbent for copper uptake but it requires the incorporation of specific functionalities to enhance the uptake and selectivity. Branched polyethylenimine (PEI) is a specific copper chelate agent but its bulky structure hinders the loading on mesoporous supports. In this work, the incorporation of PEI on a hierarchical porous silica with wrinkled meso/macroporosity (w-SiO2) resulted in a smart adsorbent with higher copper adsorption capacity. After the uptake, the annealing of the adsorbed PEI-copper complex leads to a w-SiO2/CuO nanocomposite with outstanding antimicrobial properties and catalytic activity due to the enhanced copper bioavailability. The minimum inhibitory concentration of supported copper oxide on silica for E. coli in LB broth medium was 825.5 μg Cu/ml. Oxidation of the electron donor molecule ABTS in the presence of this nanocomposite and H2O2 is a first demonstrator of the potential application as a peroxidase-like nanozyme. The use of adsorbents with hierarchical porosity to support bulky functionalities with high selectivity is a novel strategy for heavy metals upcycling.