Interlayer-Confined Molecular Assembly Enables a Family of Two-Dimensional Room-Temperature Ferromagnets.

Two-dimensional (2D) molecular ferromagnets with robust room-temperature magnetism remain elusive due to weak intermolecular interactions and structural instability. Herein, we present an interlayer-confined molecular assembly strategy to construct a family of 2D room-temperature molecular ferromagnets within metallic van der Waals (vdW) hosts. Using cobaltocene-intercalated TaS2 as a prototype, we achieve precise molecular orientation control and enhanced spin alignment through vdW confinement. Strong organic-inorganic interfacial coupling mediates itinerant-electron-driven ferromagnetic exchange, resulting in long-range ferromagnetic order above 300 K and a notable negative magnetoresistance (-5.7% at 300 K). The strategy is applicable to multiple metallic transition-metal dichalcogenides, establishing a general approach to molecularly engineered 2D spintronic materials. This work highlights the power of confined molecular assembly in discovering 2D ferromagnets and functionalizing magnetic small molecules.