Metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) as a functional precursor with structure tunability, high porosities and large surface areas, make them outstanding candidates for various applications. Prussian blue and its analogues (PB/PBAs), A_xM[Fe(CN)₆]_y·nH₂O (0 < x ≤ 2, 0 < y ≤ 1), are promising porous materials. PBAs/MOFs can be converted into metal, metal compounds (e.g. metal oxide, metal phosphide, metal sulfide), carbon materials and their derived composites (P/MDCs) for various applications including separation, sensing, heterogeneous catalysis, hydrogen storage, medicine and energy storage. PB/PBA can undergo ion exchange process, leading to the formation of various compounds such as metal hydroxides and oxyhydroxides. It's worth noting that PBAs can form a series of controlled, stable, nano-scale, polycrystalline metal oxide particles under hydrothermal conditions, which is different from traditional alkaline etching products. Nonetheless, the transformation mechanism of P/MDCs in hydrothermal process, is still unclear. The effects and interrelationships of the different conditions of P/MDCs in liquid phase are yet to be established. Therefore, this is of significance to explore the transformation mechanism of P/MDCs in hydrothermal process for various applications.

Recently, Pang's group studied the coordination structure changes and crystal phase transformation mechanisms of PBAs crystals during hydrothermal processes. By analyzing a large number of synthesis conditions and parameters, the phase diagram and machine learning model of PBA in hydrothermal reaction have been established. The correlations among 9 parameters during phase transformation of P/MDCs in hydrothermal process were analyzed in terms of five dimensions “S-P-A-C-E”, the synthesis, phase, architecture, characteristics, and electrochemical properties. Subsequently, thirty-one FeO_x-NP@PBA were precisely fabricated by increasing from binary- to high quaternary- metals precursors. More importantly, P/MDCs with specific crystalline phases can be precisely regulated and directionally prepared according to the phase diagram. This research has provided a unified model for the synthesis P/MDCs in hydrothermal process, and it is expected to establish the basis for the qualitative preparation of other composites.

Research Article: Guangxun Zhang, Yibo Lu, Ya Yang, Hui Yang, Zilin Yang, Shixian Wang, Wenting Li, Yangyang Sun, Jianfei Huang, Yongsong Luo, Han-Yi Chen, Yen-Fa Liao, Hirofumi Ishii, Sanna Gull, Mohsen Shakouri, Huai-Guo Xue, Yongfeng Hu, and Huan Pang*, Dynamic Phase Transformations of Prussian Blue Analogue Crystals in Hydrotherms. J. Am. Chem. Soc., 2024, DOI: 10.1021/jacs.4c03827.

Web Link：https://doi.org/10.1021/jacs.4c03827