CCR review on spin crossover Hofmann-type MOFs

Hofmann-type metal-organic frameworks (MOFs), built from FeII centers, cyanometallate nodes and organic ligands, represent a prototypical class of porous coordination polymers. Their modular architecture allows precise tuning of dimensionality and ligand fields, enabling controllable spin crossover in response to temperature, pressure, light, or guest adsorption. This review first outlines recent advances in the synthesis of Hofmann-type MOFs across different material forms, from single crystals to thin films and nanoscale systems. The spin crossover behavior of both two-dimensional (2D) and three-dimensional (3D) systems, is then examined, highlighting how cooperative elastic interactions, host-guest effects, weak intermolecular forces, and external stimuli govern transition profiles. Beyond magnetic properties, the integration of multifunctionality is discussed, where spin-state switching is coupled with optical, redox, dielectric, and electrical responses. Special attention is given to emerging applications in gas adsorption and separation, and catalysis. Finally, practical challenges related to structural stability, reversibility, and processability, are addressed and future directions are outlined for the rational design and scalable implementation of spin crossover-based frameworks as next-generation stimuli-responsive functional materials.

Authors: Weiyang Li, Shubiao Xia, Jianjun Liu, Yanfeng Bi, Xiaochun Li, Yann Garcia

FeII based spin crossover Hofmann-type MOFs: Recent progress in spin state regulation, multifunctionality and applications, Coordination Chemistry Reviews, Volume 566, Part 2, 2026,
218195, ISSN 0010-8545, https://doi.org/10.1016/j.ccr.2026.21819