Synthesis, Structural Investigation, and Energetic Performance Study of ZIF-25

Abstract

The synthesis of ZIF-25 was successfully optimized by using acetic acid as a modulator agent, yielding a highly crystalline material. The product exhibits significant porosity, thermal stability up to 300 °C, and hydrophobicity, making it ideal for use in lyophobic heterogeneous systems (LHSs). Notably, the crystal structure of ZIF-25 was refined for the first time using the Rietveld method and fully reported in space group Pm3̅m. Energetic performance evaluation in intrusion–extrusion experiments shows that the “ZIF-25–water” system dissipates mechanical energy with adsorbed and released energies of ∼15–19 and ∼10 J g^–1, respectively. These features make it an LHS with shock-absorber characteristics. The study highlights that the energetic behavior of ZIFs is topology-dependent, with RHO-type ZIFs such as ZIF-25 and ZIF-71 showing shock-absorber properties, while SOD-type ZIFs (like ZIF-8) exhibit spring-like behavior. Post-experiment characterizations, performed by X-ray diffraction, nitrogen adsorption at 77 K, and scanning electron microscopy, indicate moderate and pressure-dependent degradation when the material is subjected to pressurized water intrusion.