Perusing redox nanozymes capable of disrupting cellular homeostasis offers new opportunities to develop cancer-specific therapy, but remains challenging, because most artificial enzymes lack enzyme-like scale and configuration. Herein, for the first time, we leverage a defect engineering strategy to develop a simple yet efficient redox nanozyme by constructing enzymemimicking active centers and investigated its formation and catalysis mechanism thoroughly. Specifically, the partial Fe doping in MoO x (donated as Fe-MoO v ) was demonstrated to activate structure reconstruction with abundant defect site generation, including Fe substitution and oxygen vacancy (OV) defects, which significantly enable the binding capacity and catalytic activity of Fe-MoO v nanozymes in a synergetic fashion. More intriguingly, plenty of delocalized electrons appear due to Fe-facilitated band structure reconstruction, directly contributing to the remarkable surface plasmon resonance effect in the near-infrared (NIR) region. Under NIR-II laser irradiation, the designed Fe-MoO v nanozymes are able to induce substantial disruption of redox and metabolism homeostasis in the tumor region via enzyme-mimicking cascade reactions, thus significantly augmenting therapeutic effects. This study that takes advantage of defect engineering offers new insights into developing high-efficiency redox nanozymes.

A series of vanadium doped Fe2O3 catalysts were synthesized using the homogeneous precipitation method and subjected to laboratory evaluation for selective catalytic reduction of NO x with NH3 (NH3-SCR). The best Fe0.75V0.25Oδ catalyst with a Fe/V mole ratio of 3/1 exhibited superior catalytic performance, achieving 100% NO x conversion at 200 °C over a wide temperature window from 175 to 400 °C, believed to be the best Fe-based low-temperature NH3-SCR catalyst identified to date. The Fe0.75V0.25Oδ catalyst also showed prominent resistance to high gas hourly space velocity (GHSV; 200 000 h–1) and strong durability to SO2 and H2O. Doping of V was shown to remarkably boost the catalytic activity, due to enhancement of the redox ability and surface acidity. XRD, Raman, and morphology results revealed that the incorporation of V had led to the formation of amorphous FeVO4 and Fe2O3. Coupling XPS and UV–vis diffuse reflectance spectra (DRS) results with DFT, it was discovered that the electron inductive effect between Fe and V generated the charge depletion of Fe, resulting in an improvement of the redox ability, facilitating the oxidation of NO to NO2. Meanwhile, the strong interaction between FeVO4 and Fe2O3 species kept V at a higher valence, beneficial for the adsorption and activation of NH3. The synergistic effect of FeVO4 and Fe2O3 thus improved the low-temperature catalytic activity and lowered the apparent activation energy. Combining in situ diffusion Fourier transform infrared spectroscopy (DRIFTS) results with reaction kinetic studies, it was concluded that the SCR reaction mainly followed the Langmuir–Hinshelwood mechanism below 200 °C, since the consumption of adsorbed NH3 species could be divided into the explicit “standard SCR” and “fast SCR” stages, while an Eley–Rideal mechanism proceeded dominantly at and above 200 °C, in which the adsorbed NH3 species were eliminated by gaseous NO directly and linearly. Both the Brønsted and Lewis acid sites played equivalently significant roles in NH3-SCR reaction.

A concise first total synthesis of (±) maoecrystal V (1) is reported. The synthesis features a Wessely oxidative dearomatization of a phenol, an intramolecular Diels-Alder reaction, and a Rh-catalyzed O-H bond insertion as key steps.