Photocatalysis technology has the advantages of being green, clean, and environmentally friendly, and has been widely used in CO₂ reduction, hydrolytic hydrogen production, and the degradation of pollutants in water. Cu₂O has the advantages of abundant reserves, a low cost, and environmental friendliness. Based on the narrow bandgap and strong visible light absorption ability of Cu₂O, Cu₂O-based composite materials show infinite development potential in photocatalysis. However, in practical large-scale applications, Cu₂O-based composites still pose some urgent problems that need to be solved, such as the high composite rate of photogenerated carriers, and poor photocatalytic activity. This paper introduces a series of Cu₂O-based composites, based on recent reports, including pure Cu₂O and Cu₂O hybrid materials. The modification strategies of photocatalysts, critical physical and chemical parameters of photocatalytic reactions, and the mechanism for the synergistic improvement of photocatalytic performance are investigated and explored. In addition, the application and photocatalytic performance of Cu₂O-based photocatalysts in CO₂ photoreduction, hydrogen production, and water pollution treatment are discussed and evaluated. Finally, the current challenges and development prospects are pointed out, to provide guidance in applying Cu₂O-based catalysts in renewable energy utilization and environmental protection.

The pollution of phenol wastewater is becoming worse. In this paper, a 2D/2D nanosheet-like ZnTiO₃/Bi₂WO₆ S-Scheme heterojunction was synthesized for the first time through a two-step calcination method and a hydrothermal method. In order to improve the separation efficiency of photogenerated carriers, the S-Scheme heterojunction charge-transfer path was designed and constructed, the photoelectrocatalytic effect of the applied electric field was utilized, and the photoelectric coupling catalytic degradation performance was greatly enhanced. When the applied voltage was +0.5 V, the ZnTiO₃/Bi₂WO₆ molar ratio of 1.5:1 had highest degradation rate under visible light: the degradation rate was 93%, and the kinetic rate was 3.6 times higher than that of pure Bi₂WO₆. Moreover, the stability of the composite photoelectrocatalyst was excellent: the photoelectrocatalytic degradation rate of the photoelectrocatalyst remained above 90% after five cycles. In addition, through electrochemical analysis, XRD, XPS, TEM, radical trapping experiments, and valence band spectroscopy, we found that the S-scheme heterojunction was constructed between the two semiconductors, which effectively retained the redox ability of the two semiconductors. This provides new insights for the construction of a two-component direct S-scheme heterojunction as well as a feasible new solution for the treatment of phenol wastewater pollution.

A simple, sensitive colorimetric probe for detecting Cu(II) ions with fast response has been established with a detection limit of 2.82 μM. UV-Vis spectroscopy along with metal ion response, selectivity, stoichiometry, competition was investigated. In the presence of copper(II), the UV-Vis spectrum data showed significant changes and the colorimetric detection showed a color change from colorless to yellow. After the selective binding of receptor L with Cu(II), the UV-visible absorption at 355 nm decreased dramatically, a new absorbance band appeared at 398 nm and its intensity enhanced with the increase in the amount of Cu(II). Moreover, it exhibited highly selective and sensitive recognition towards Cu(II) ions in the presence of other cations over the pH range of 7–11. The complex structure was verified by FT-IR spectroscopy, elemental analysis and quantum mechanical calculations using B3LYP/6-31G(d) to illustrate the complex formation between L and Cu(II). According to the Job plot and the quantum mechanical calculations, the stoichiometric ratio for the complex formation was proposed to be 1 : 1.

Three boron-pyridyl-isoindoline-1-one based dyes (B1, B2, and B3) with varied side groups were facilely synthesized. Detailed analyses were carried out concerning the crystal conformation, structure dependent photophysical properties and mechanochromic fluorescence (MCF). The MCF behaviours and solid-state emission were demonstrated to be correlated to the different side groups. Upon grinding, the emission of B1 exhibited little changes, whereas reversible MCF with a distinct colour change was observed for B2 and B3. B3 possessing sterically hindered triphenyl amine (TPA) groups showed the most prominent MCF effect. For instance, mechanical grinding resulted in a red-shift of fluorescence from 600 nm to 650 nm. The electronic and steric effects of the donating substituents were found to play important roles in modulating the intramolecular charge-transfer effect and intermolecular interactions. These sensitively and readily tunable mechano-responsive behaviors of the boron-pyridyl-isoindoline-1-one based dyes make them potential candidates for smart fluorescent materials.