Green Oxidative Degradation of Methyl Orange with Copper(II) Schiff Base Complexes as Photo‐Fenton‐Like Catalysts

Abstract

Two copper(II) complexes, namely [Cu(HL)Cl] (1) and [Cu(HL)Br](2),whereHListhemultidentateSchiffbaseN-[(2-oxy-acetate)benzyl]-2-aminothanol, were synthesized and fully characterized. The Cu II ions in 1 and 2 are pentacoordinate and the coordination arrangement is best described as distorted square-pyramidal. The degradation

Degradation of Methylene Blue with a Cu(II)–Quinoline Complex Immobilized on a Silica Support as a Photo-Fenton-Like Catalyst

“…The catalysis takes place on the surface of the silica particles, where the active site of the [L–Cu 2+ ] complex was immobilized. The unsaturated [L–Cu 2+ ] complex could bind peroxide to form [L–Cu 2+ ( − O 2 H)] (pathway (1)), which can subsequently transform into a peroxo complex [L–Cu + (O 2 H) • ] as a result of charge transfer between a hydroperoxide anion ( − O 2 H) and Cu 2+ (pathway (2)). , The peroxo complex can then react with H 2 O 2 to produce HO • radicals (pathway (4)). − The [L–Cu 2+ ( − O 2 H)] can also be regarded as an oxidant based on a complex mechanism, directly oxidizing substrates through pathway (6). , In addition, the copper redox cycle with HO • and the production of dissolved O 2 (pathway (4)) are likely to involve a catalytic cycle (pathways (7) and (8)). ,− During these processes, the substrate in the reaction can be excited (pathway (9)), transferring an electron to the metal-centered orbitals (pathway (10)) with this substrate to the metal charge transfer (SMCT) process contributing to the decolorization of the substrate via the loss of conjugation of the double bonds in the molecule . With photo assistance, the photoreduction of Cu 2+ to Cu + occurs through charge transfer between the ligand and the metal.…”

Two multifunctional Cu(ii) coordination complexes with mixed ligands as efficient catalysts for the oxygen evolution reaction and photocatalytic degradation of methyl orange azo dyes

“…51,52 In addition, the e − also combines with O 2 in the system to form super-oxide radicals (˙O 2 − ). 53 Moreover, Fei 54 and Wang 55 demonstrated that ˙OH, O 2 − and h + are the main reactive species during the degradation of MO. So, the degradation mechanism of MO can be expressed by the following reactions: 56,57 1 or 2 + hv → h + + e − h + + H 2 O or H 2 O 2 → ˙OH + H + e − + O 2 → ˙O 2 − ˙OH or ˙O 2 − + MO → Products…”

Alkaline-Stable Peroxidase Mimics Based on Biological Metal–Organic Frameworks for Recyclable Scavenging of Hydrogen Peroxide and Detecting Glucose in Apple Fruits

“…MOFs, which are supermolecular or three-dimensional extended periodic network structures, can be diversely tailored by the judicious selection of metal ion and organic ligand building blocks to achieve required properties. , They provide a coordination environment similar to that of natural enzymes owing to their adjustable cavities and channels, making them have potential applications in drug delivery, thermal insulation, separation, and filtration. − MOFs have been recently reported to show a high peroxidase-like catalytic activity in the pH range of 3–10 and have been employed as colorimetric biosensors, thereby further expanding the scope of analytical applications. ,− The most pervasive biosensors take advantage of the Cu-based MOFs, which undergo the Fenton-like reaction in the presence of hydrogen peroxide. , H 2 O 2 can be activated by Cu 2+ to generate active oxygen species, such as • OH, • OOH, and O 2 •– , in a copper-catalyzed Fenton-like system . The hydroxyl radical ( • OH) generated from the activation of H 2 O 2 has a strong oxidation potential; thus, various activation schemes have been used for degrading organic contaminants into harmless compounds, low-molecular-weight organic acids, inorganic salts, and water. , An increasing number of studies have demonstrated that the Cu-based MOFs with appropriate ligands may significantly improve the catalytic activities of Cu 2+ and increase the effectiveness in decomposing organic compounds, as well as scavenging H 2 O 2 . , In addition, with the catalytic system of Cu-MOFs and H 2 O 2 , the colorless peroxidase substrate 3,3′,5,5′-tetramethyl-benzidine (TMB) and 2,2′-azino-bis­(3-ethylbenzothiazoline-6-sulfonate) (ABTS) are oxidized to blue oxTMB and green oxABTS, respectively. , The color-changing process can be observed by naked eyes, enabling such MOFs to be used as eye-probes of H 2 O 2 . Thus, the system based on the Fenton-like reaction and oxidation of the peroxidase substrate provides a convenient colorimetric signal transition strategy for constructing bioanalytical methods.…”

“…22,23 An increasing number of studies have demonstrated that the Cubased MOFs with appropriate ligands may significantly improve the catalytic activities of Cu 2+ and increase the effectiveness in decomposing organic compounds, as well as scavenging H 2 O 2 . 24,25 In addition, with the catalytic system of Cu-MOFs and H 2 O 2 , the colorless peroxidase substrate 3,3′,5,5′-tetramethyl-benzidine (TMB) and 2,2′-azino-bis(3ethylbenzothiazoline-6-sulfonate) (ABTS) are oxidized to blue oxTMB and green oxABTS, respectively. 10,26 The colorchanging process can be observed by naked eyes, enabling such MOFs to be used as eye-probes of H 2 O 2 .…”