Screening of natural deep eutectic solvents and their application in FOX-7 recrystallization

To screen green solvents suitable for the recrystallization of FOX-7, this study combined the conductor-like screening model for real solvents (COSMO-RS) theory with experimental methods to identify applicable natural deep eutectic solvents (NADES). The structural correlations of their dissolution performance were analyzed based on quantum chemical parameters, including σ-profiles, electrostatic potential maps, and dipole moments. The selected NADES were then prepared and characterized in terms of their structure and thermal stability, and their feasibility as recrystallization solvents for FOX-7 was further evaluated. The results showed that the screened NADES met the requirements for FOX-7 recrystallization, with betaine–lactic acid (1:2) and choline chloride–urea (1:2) exhibiting FOX-7 solubilities of 0.11 g mL −1 and 0.073 g mL −1 at 76 °C and 78 °C, respectively. Hydrogen bond acceptors in high-solubility NADES generally featured larger σ-profile dual-peak spacing and dipole moments exceeding 10 Debye, with the systems mainly forming stable molecular clusters through hydrogen bonding and van der Waals interactions. These findings provide a theoretical basis for the design of NADES and the development of green crystallization systems for energetic materials.