Two-Dimensional Metal–Organic Framework with High-Performance Single-Molecule Magnets as Nodes Showing Magnetic Coercivity Photomodulation

Addressing the spatial organization of high-performance single-molecule magnets (SMMs) and achieving stimuli-responsive switching of their magnetic bistability are pivotal challenges in molecular memory technologies, paving the way for advanced opto-magnetic devices. Herein, we utilize the photosensitive ligand 4,4'-bipyridine (BPy) as a linker to incorporate typical pentagonal-bipyramidal SMMs as nodes into a two-dimensional metal-organic framework (MOF), formulated as {[Dy_1.5(OPh)₂Cl(BPy)₃(THF)_1.5][(BPh₄)_1.5]·0.5THF}_<i>n</i> (<b>1</b>). The precise synthesis facilitates axial coordination of PhO^- and equatorial alignment of BPy, enforcing perpendicular orientations of the principal magnetic axes of Dy³⁺ ions across all Kagomé layers. Compound <b>1</b> exhibits photochromic behavior upon exposure to ultraviolet irradiation at room temperature, driven by a photoinduced electron transfer process that generates radicals. The resulting <b>1uv</b> displays overall faster relaxation dynamics compared to <b>1</b>, characterized by shorter relaxation times at identical temperatures within the 12-70 K range, a lower diverging temperature in field-cooled and zero-field-cooled curves (9 K for <b>1</b> vs. 6 K for <b>1uv</b>), and reduced energy barriers from 1048(17)/822(46) K for <b>1</b> to 1000(9)/641(34) K for <b>1uv</b>. Notably, the coercive field decreases dramatically from 4500 Oe for <b>1</b> to 1300 Oe for <b>1uv</b> at 2 K, while the hysteresis loop opening temperature decreases from 20 K for <b>1</b> to 14 K for <b>1uv</b>. These photoinduced changes are due to the formation of photogenerated radicals and alterations in crystal packing. This work achieves an MOF that integrate high-performance SMM behavior with magnetic coercive photomodulation, providing a design paradigm for engineering advanced SMM-MOFs with tailored photomagnetic switching.