In this work, the application of advanced oxidation processes (AOPs) for the removal of antibiotics from water has been reviewed. The present concern about water has been exposed, and the main problems derived from the presence of emerging pollutants have been analyzed. Photolysis processes, ozone-based AOPs including ozonation, O3/UV, O3/H2O2, and O3/H2O2/UV, hydrogen peroxide-based methods (i.e., H2O2/UV, Fenton, Fenton-like, hetero-Fenton, and photo-Fenton), heterogeneous photocatalysis (TiO2/UV and TiO2/H2O2/UV systems), and sonochemical and electrooxidative AOPs have been reviewed. The main challenges and prospects of AOPs, as well as some recommendations for the improvement of AOPs aimed at the removal of antibiotics from wastewaters, are pointed out.

Advanced Oxidation Processes for the Removal of Antibiotics from Water. An Overview

Visible light photocatalytic degradation of tetracycline over TiO2

The synthesis strategies and photocatalytic performances of TiO2/MOFs composites: A state-of-the-art review

Fabrication of visible-light-active MR/NH2-MIL-125(Ti) homojunction with boosted photocatalytic performance

In this review, we discuss the progress in the preparation methods and diverse applications for covalent triazine frameworks, hypercrosslinked polymers, covalent organic frameworks, and conjugated microporous polymers. 

Advances in porous organic polymers: syntheses, structures, and diverse applications

TiO2 is the most established semiconductor photocatalyst. The prominence of TiO2 is becoming increasingly obvious because its interfacial redox reactions have implication on a wide range processes such as energy conversion and environmental remediation. Herein, we exploited the surface complex created by the interaction between organic molecules with binding sites and accommodating surface of TiO2 for visible light-driven selective aerobic oxidation reactions. A novel surface complex formed between N-hydroxyphthalimide (NHPI) and TiO2 was discovered. The NHPI-TiO2 complex turned out to be an outstanding visible light photocatalyst and was successfully used in the selective oxidation of amines into imines with atmosphere O2 under blue LED irradiation. The stability of the NHPI-TiO2 complex was preserved by 3 mol% of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) acting as a cooperative catalyst. Moreover, selectivities for the imine products were also promoted by TEMPO. Superoxide anion radical (O2 −) were evidenced to be the primary reactive oxygen species (ROS) to execute the oxidative conversions. This work suggests that TiO2 surface complexes can be robust photocatalysts for visible light-driven selective aerobic reactions, provided that an appropriate cooperative redox catalyst exists to channel the photocatalytic electron transfer.

N-hydroxyphthalimide-TiO2 complex visible light photocatalysis

The interplay of salicylic acid (SA) and reactive oxygen species (ROS) can modulate biotic and abiotic stress of plants, essential biological aerobic oxidation processes. Meanwhile, ROS plays a critical role in TiO2 photocatalytic system for the degradation of organic species. Herein, we developed a system consisted of SA and TiO2 aiming at the selective oxidation of organic molecules by ROS. Interestingly, SA complexed with TiO2 leads to ligand-to-metal charge transfer (LMCT) under visible light irradiation. The charge transfer from ligand (chemically adsorbed SA) to metal (conduction band of TiO2) activates O2 to ROS, superoxide (O2 −). The positive charge located at ligand SA is connected with (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) catalysis for direct two-electron oxidation of amines and later regenerated by O2 −. SA and its derivatives were screened as ligands of TiO2 for the selective aerobic oxidation of amines into imines under blue light-emitting diode (LED) irradiation in which 5-CH3O-SA (5-methoxysalicylic acid, 0.8 mol%) complexed with anatase TiO2 and coupled with TEMPO (5 mol%) confers significantly better results than the others. By this visible light LMCT route, both primary amines and secondary amines can be selectively oxidized into corresponding imines with atmosphere O2 as the terminal oxidant. Importantly, the desired product of N-benzylidenebenzylamine can be isolated in 92% yield.

Salicylic acid complexed with TiO2 for visible light-driven selective oxidation of amines into imines with air

TEMPO visible light photocatalysis: The selective aerobic oxidation of thiols to disulfides

Conjugated microporous polymers (CMPs) have been showcased with a brilliant prospect in organic semiconductor photocatalysis, attributing to accessible molecular design, chemical stability and environmental friendliness. Here, two novel fluorene-based CMPs were designed and conveniently synthesized with carbazole as an electron donor. Importantly, subtle variation of substituent at the methylene bridge (9-position) of fluorene precursor results in different performances in which dimethyl substituent was proven to be more efficient than difluoro substituent for blue light photocatalysis. MFC [9,9'-(9,9-dimethyl-9H-fluorene-2,7-diyl)bis(9H-carbazole)]-CMP has a much larger specific surface area, a more favourable redox position, and resultantly a superior photocatalytic performance during blue light-driven selective oxidation of amines into imines with oxygen (O2) in an environmentally benign solvent ethanol (C2H5OH). This work suggests that subtle tweaking in electron acceptors could give rise to superior photocatalytic activity for CMPs in selective chemical conversions.

Hui Xu

Papers

N-hydroxyphthalimide-TiO2 complex visible light photocatalysis

Salicylic acid complexed with TiO2 for visible light-driven selective oxidation of amines into imines with air

TEMPO visible light photocatalysis: The selective aerobic oxidation of thiols to disulfides

Designing fluorene-based conjugated microporous polymers for blue light-driven photocatalytic selective oxidation of amines with oxygen

Visible-light photocatalytic selective aerobic oxidation of thiols to disulfides on anatase TiO2