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Metal-containing Fenton catalysts have been widely investigated. Here, we report for the first time a highly effective stable metal-free Fenton-like catalyst with dual reaction centers consisting of 4-phenoxyphenol-functionalized reduced graphene oxide nanosheets (POP-rGO NSs) prepared through surface complexation and copolymerization. Experimental and theoretical studies verified that dual reaction centers are formed on the C-O-C bridge of POP-rGO NSs. The electron-rich center around O is responsible for the efficient reduction of H2O2 to •OH, while the electron-poor center around C captures electrons from the adsorbed pollutants and diverts them to the electron-rich area via the C-O-C bridge. By these processes, pollutants are degraded and mineralized quickly in a wide pH range, and a higher H2O2 utilization efficiency is achieved. Our findings address the problems of the classical Fenton reaction and are useful for the development of efficient Fenton-like catalysts using organic polymers for different fields. [ABSTRACT FROM AUTHOR]

Carbon nitride compounds (CN) complexed with the in-situ-produced Cu(II) on the surface of CuAlO 2 substrate (CN-Cu(II)-CuAlO 2 ) is prepared via a surface growth process for the first time and exhibits exceptionally high activity and efficiency for the degradation of the refractory pollutants in water through a Fenton-like process in a wide pH range. The reaction rate for bisphenol A removal is ∼25 times higher than that of the CuAlO 2 . According to the characterization, Cu(II) generation on the surface of CuAlO 2 during the surface growth process results in the marked decrease of the surface oxygen vacancies and the formation of the C-O-Cu bridges between CN and Cu(II)-CuAlO 2 in the catalyst. The electron paramagnetic resonance (EPR) analysis and density functional theory (DFT) calculations demonstrate that the dual reaction centers are produced around the Cu and C sites due to the cation-π interactions through the C-O-Cu bridges in CN-Cu(II)-CuAlO 2 . During the Fenton-like reactions, the electron-rich center around Cu is responsible for the efficient reduction of H 2 O 2 to • OH, and the electron-poor center around C captures electrons from H 2 O 2 or pollutants and diverts them to the electron-rich area via the C-O-Cu bridge. Thus, the catalyst exhibits excellent catalytic performance for the refractory pollutant degradation. This study can deepen our understanding on the enhanced Fenton reactivity for water purification through functionalizing with organic solid-phase ligands on the catalyst surface.

Mesoporous Cu-doped γ-Al2O3 (γ-Cu-Al2O3) was prepared via an evaporation-induced self-assembly process, in which Cu(+/2+) was co-incorporated into mesoporous γ-Al2O3 by chemical bonding of Al-O-Cu. The catalyst was found to be highly effective and stable for the degradation and mineralization of aromatic pollutants, as demonstrated with bisphenol A, 2,4-dichlorophenoxyacetic acid, ibuprofen, diphenhydramine, and phenytoin in the presence of H2O2 under neutral pH conditions. In addition, the high utilization efficiency of H2O2 was maintained at approximately 90% prior to the disappearance of the initial aromatic pollutants. On the basis of all of the characterization results, the pollutant degradation processes predominantly occurred on the surface of the catalyst due to the formation of σ-Cu-ligand complexes between the phenolic OH group and the surface Cu. In the reaction system, in addition to the unselective oxidation by (•)OH, H2O2 directly attacked the σ-Cu(2+)-complexes aromatic ring with the phenolic OH group, which resulted in the formation of (•)OH and HO-adduct radicals that were oxidized to hydroxylation products by reduction of Cu(2+) in the σ-Cu(2+)-complexes to Cu(+). The process prevented Cu(2+) from oxidizing H2O2 to form HO2(•)/O2(•-) or O2, and enhanced the Cu(+)/Cu(2+) cycle, the formation of (•)OH, and the utilization efficiency of H2O2. Therefore, an extraordinarily high degradation and mineralization of the aromatic pollutants was observed.