Tuning Magnetic Dimensionality via Metal‐Ion Dilution in a Polyoxometalate‐Templated 2D Framework

ABSTRACT The rational design of superparamagnetic molecular magnets remains a central challenge in molecular materials chemistry. Herein, we report a silicotungstate‐templated, 2D cyanoferrate coordination polymer and its four isostructural Zn 2+ ‐diluted analogs, {(SiW 12 O 40 )@[TpFe(CN) 3 ] 2 Fe 3‐ x Zn x (MeOH) 6 ∙6MeOH} n (Tp = Tri(pyrazolyl)borate; 1 – 5 , x = 0–3). The neutral hybrid layers adopt a cyanide‐bridged honeycomb topology, with (SiW 12 O 40 ) 4– anions located in the cavities and interlayer metal‐to‐metal separations exceeding 10 Å. Magnetic study revealed that 1 ( x = 0) behaves as a metamagnet with an ordering temperature of 15.5 K, featuring intralayer ferromagnetic and interlayer antiferromagnetic coupling. Remarkably, Zn 2+ doping disrupts the 2D magnetic layer, triggering a dimensional crossover in magnetism. As a result, compounds 2 ( x = 0.41) and 3 ( x = 0.93) exhibit slow relaxation of the magnetization, suggesting a superparamagnetic behavior, with effective energy barriers of 40.9 and 46.3 K, respectively. This transition from 2D to lower‐dimensional magnetism arises from a fragmentation of the honeycomb network into isolated spin chains (clusters) via metal‐ion dilution. Such a metal‐doping‐induced “top‐down” transformation of magnetic dimensionality provides a novel alternative to conventional bottom‐up synthetic strategies for engineering low‐dimensional magnetic materials.