Cu2O@β-cyclodextrin as a synergistic catalyst for hydroxyl radical generation and molecular recognitive destruction of aromatic pollutants at neutral pH.

Wastewater systems contain a large number of compounds, such as anthropogenic aromatic pollutants and natural organic matter (NOM), and usually have pH higher than 4. Fenton-like reaction is the most widespread method for removal of organic pollutants, but their reactivity with H2O2 may be inhibited by NOM due to the competition of hydroxyl radicals and chelating agents. In this work, Cu2O@β-cyclodextrin was developed to achieve the collaboration between molecular recognition and Fenton-like catalysis to destruct aromatic pollutants at neutral pH. In Cu2O@β-CD, covalent CuOC bond was topotaxially converted from CuCl assisted by β-CD at room temperature. Covalently linked β-CD could keep humic acid from interfering catalytic performance of Cu2O surfaces and inhibit the leaching of copper. A higher catalytic ability was observed for Cu2O@β-CD with rate constant 0.0331 min-1 than Cu2O (0.0064 min-1) at neutral pH. A mechanism of synergistic catalysis was proposed on the basis of Cu+, β-CD and phenoxo-Cu2+ complexes in the Cu2O@β-CD/BPA/H2O2 system. The strategy of coupling molecular recognition into Fenton-like reaction provides an efficient and promising approach to the destruction of aromatic pollutants at neutral pH.