Mechanically responsive metal–organic frameworks (MOFs) came very recently into the spotlight of material science for their unique properties and potential new fields of application. We present here a clarification of the magnetic properties of prototypical magnetic MOF-74 material, Ni(II)-MOF-74, using magnetization measurements, X-band electron spin resonance (ESR), multi-frequency high-field ESR (HF-ESR), and theoretical model. It was established that the guests populating the honeycomb channels have little influence on the magnetism of Ni-MOF-74, whereas magnetic properties change significantly upon mechanical amorphization. Amorphous material (am-Ni-MOF-74), which can be readily prepared by the mechanochemical treatment of dehydrated Ni-MOF-74 (deh-Ni-MOF-74), as shown by in situ monitoring methods, displays significantly lower bulk magnetization compared to Ni-MOF-74 and deh-Ni-MOF-74. This decline in magnetization is established to be a consequence of the spin-crossover from high-spin to a low-spin state of nickel(II) ions. The observed spin-crossover was rationalized by an insight into the changes of the nickel coordination sphere during the amorphization, which was provided by solid-state nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. Additionally, it was found that am-Ni-MOF-74 behaves differently than its zinc analogue when exposed to vapors or liquid-additives in the milling process, indicating that the nature of the metal node plays a substantial role in the mechanical properties of this modular family of MOF materials.

Plasma-activated water (PAW) is a liquid enriched with reactive oxygen and nitrogen species (RONS), which impart antimicrobial and bioactive properties. In this study, PAW generated in liquid or gas phase under nitrogen or oxygen atmospheres was characterized in terms of pH, electrical conductivity, oxidation-reduction potential, surface tension, and concentrations of H₂O₂ and NO₂⁻. Hydroxyl radical (•OH) formation was confirmed using DIPPMPO as a spin-trapping probe, while antioxidant activity was determined directly in treated water for the first time. The stability of reactive species was assessed over three months at room temperature, 4 °C, and −18 °C. Results indicate that plasma effects on physicochemical parameters depend strongly on the process gas. From a long-term storage perspective, samples maintained at 4 °C stabilized at higher H₂O₂ and NO₂⁻ concentrations. Antioxidant activity persisted for up to 60 days, though at low levels. EPR analysis revealed that hydroxyl radical concentration increased slightly during storage, with 60-day samples showing higher signal intensities compared to fresh PAW. Overall, the findings provide new insights into PAW composition, radical dynamics, and stability, highlighting the influence of gas atmosphere and storage conditions on its properties and supporting its potential for applications in the food, agriculture, and biomedical sectors.