Benefiting from the unique electronic and structural characteristics, transition metal and nitrogen co-doped carbon-based (M–N–C) nanomaterials are considered to be one of the most promising catalysts. The combination of uniformly dispersed Cu sites and N-doped carbon materials has enabled Cu–N–C SACs to show outstanding performances in many catalytic fields. However, the adjustment of their coordination environment, the influence of carrier materials and their dynamic evolution in the catalytic process still remain unclear, which limits the application of Cu–N–C SACs. Thus, it is of great significance and urgent to deeply understand the reaction mechanism of Cu–N–C SACs in different catalytic fields. This review focuses on the preparation strategy, regulation mechanism of the coordination environment, catalytic performance and dynamic evolution process of Cu–N–C SACs. Combined with a series of in situ/operando characterization methods, the changes in their coordination and structure in the catalytic process is highlighted. Finally, the prospects of active machine learning, coordination structure identification and determination of real active sites are presented. This review aims to provide a reference for the rational design of Cu–N–C SACs and the exploration of their catalytic mechanism.

Coarse wool is a kind of goat wool that is difficult to further process in the textile industry due to its large diameter, dispersion, better strength, and less bending. Therefore, coarse wool is often discarded as waste or made into low-cost products. In this work, keratin was extracted from coarse wool by a high-efficiency method, and then, an Ag-doped keratin/PA6 composite nanofiber membrane with enhanced filtration and antibacterial performance was prepared using HCOOH as solvent and reductant. HAADF-STEM (high-angle annular dark field-scanning transmission electron microscopy) shows that AgNPs are uniformly distributed in keratin/PA6 (30/70) nanofibers. TGA (Thermogravimetric Analysis) and DSC (Differential Scanning Calorimetry) were employed to investigate the thermal stability of composite membranes with different keratin and AgNP contents. The present keratin as a dopant with polyamide-6 (PA6) was found not only to improve air filtration efficiency but also to enhance water–vapour transmission (WVT). The addition of the Ag nanoparticles (AgNPs) gave a strong antibacterial activity to the composite membrane against Staphylococcus aureus (99.62%) and Escherichia coli (99.10%). Bacterial filtration efficiency (BFE) of the composite membrane against S. aureus and E. coli were up to 96.8% and 95.6%, respectively. All of the results suggested a great potential for coarse wool extraction and application in the air filtration field.

An original Von Koch curve-shaped tipped electrospinneret was used to prepare a polyimide (PI)-based nanofiber membrane. A multilayer Al₂O₃@polyimide/polyethylene/Al₂O₃@polyimide (APEAP) composite membrane was tactfully designed with an Al₂O₃@ polyimide (AP) membrane as outer shell, imparting high temperature to the thermal run-away separator performance and a core polyethylene (PE) layer imparts the separator with a thermal shut-down property at low temperature (123 °C). An AP electrospun nanofiber was obtained by doping Al₂O₃ nanoparticles in PI solution. The core polyethylene layer was prepared using polyethylene powder and polyterafluoroethylene (PTFE) miniemulsion through a coating process. The addition of PTFE not only bonds PE power, but also increases the adhesion force between the PE and AP membranes. As a result, the multilayer composite separator has high safety, outstanding electrochemical properties, and better cycling performance as a lithium-ion battery separator.

Photothermal conversion materials have attracted wide attention due to their efficient utilization of light energy. In this study, a (GO)/Bi₂S₃-PVDF/TPU composite nanofiber membrane was systematically developed, comprising GO/Bi₂S₃ nanoparticles (NPs) as a photothermal conversion component and PVDF/TPU composite nanofibers as the substrate. The GO/Bi₂S₃ NPs were synthesized in a one-step way and the PVDF/TPU nanofibers were obtained from a uniformly mixed co-solution by electrospinning. GO nanoparticles with excellent solar harvesting endow the GO/Bi₂S₃-PVDF/TPU membrane with favorable photothermal conversion. In addition, the introduction of Bi₂S₃ NPs further enhances the broadband absorption and photothermal conversion properties of the GO/Bi₂S₃-PVDF/TPU composite membrane due to its perfect broadband absorption performance and coordination with GO. Finally, the results show that the GO/Bi₂S₃-PVDF/TPU composite membrane has the highest light absorption rate (about 95%) in the wavelength range of 400–2500 nm. In the 300 s irradiation process, the temperature changes in the GO/Bi₂S₃-PVDF/TPU composite membrane were the most significant and rapid, and the equilibrium temperature of the same irradiation time was 81 °C. Due to the presence of TPU, the mechanical strength of the composite film was enhanced, which is beneficial for its operational performance. Besides this, the morphology, composition, and thermal property of the membranes were evaluated by corresponding test methods.

Flavored cigarettes are very popular among consumers. However, many essential oils in cigarettes are lost during storage, and the utilization rate of the essential oils during use is low. Therefore, effective packaging and stable sustained release are urgently needed. In this study, a composite electrospun stable nanofiber storage material was prepared for sustained release. Polyethylene glycol, which has good heat storage properties, was selected as the heat storage material to inhibit the release of essential materials during storage. Porous graphene with good thermal conductivity and a porous structure was selected as the heat conductive component to ensure rapid and uniform release. Polyethylene glycol/porous graphene polyvinyl alcohol-mint essential oil sustained-release composite electrospun nanofibers membrane was prepared by electrospinning, and the morphology, composition, thermal properties, and sustained-release properties were tested. The results showed that the composite electrospun nanofiber membrane reduced the loss of mint oil during storage and enabled the rapid release of mint oil at high temperatures. At room temperature, the retention rate of the mint oil was still more than 90% after 120 h, and at a high temperature (75°C) the retention rate was less than 20% after 10 min; that is, 80% of the essential oil material was released within 10 min.

The deterioration of water ecology caused by the discharge of oil spill wastewater, industrial sewage, and municipal sewage has attracted wide attention worldwide. Thus, it is significant to design a simple, environmentally friendly approach to separate oil–water mixtures. In this work, three different fabrics with pH-induced wettability transition were prepared by a dip-coating process for oil and water separation. The dip-coating fabrics had the advantages of oil–water separation, photocatalytic degradation, and recycling. Polyethylene terephthalate/polyamide nonwoven fabric was used as the substrate materials of the fabric. The carboxylic acid-modified TiO₂ endowed the fabric with hydrophilicity–hydrophobicity and photocatalytic properties. The Fe₃O₄ nanoparticles obtained by the coprecipitation method provided magnetism for the fabric, facilitating the recycling of the fabric and improving the hydrophobicity of the fabric. The fabrics coated with dipping solutions were superhydrophobic in a neutral environment and hydrophilic in an alkaline environment. Among the three coated fabrics, the fabric coated with stearic acid/TiO₂-Fe₃O₄ (FST) had the most satisfying oil–water separation performance and durability. Under the neutral condition, the contact angle of the FST was 151° and the separation efficiency was 98%. Under the alkaline condition, the underwater oil contact angle of the FST was 150° and the separation efficiency was 95%. After 15 cycles, the oil–water separation rate of the FST was still higher than 90%. Due to the presence of TiO₂, the coated fabric had an exceptional performance in the photodegradation of organic pollutants (69.9%). In addition, the fabrics can be quickly recovered due to magnetism.