Guest‐Driven Light‐Induced Spin Change in an Azobenzene Loaded Metal–Organic Framework

Abstract Stimuli‐responsive materials that can be reversibly switched by light are of immense interest. Among them, photo‐responsive spin crossover (SCO) complexes have great promises to combine the photoactive inputs with multifaceted outputs into switchable materials and devices. However, the reversible control the spin‐state change by photochromic guests is still challenging. Herein, we report an unprecedented guest‐driven light‐induced spin change (GD‐LISC) in a Hofmann‐type metal–organic framework (MOF), Fe (bpn) Ag (CN) 2 2 ⋅azobenzene. (1, bpn=1, 4‐bis (4‐pyridyl) naphthalene). The reversible trans–cis photoisomerization of azobenzene guest upon UV/Vis irradiation in the solid‐state results in the remarkable magnetic changes in a wide temperature range of 10–180 K. This finding not only establishes a new switching mechanism for SCO complexes, but also paves the way toward the development of new generation of photo‐responsive magnetic materials.