Two heptanuclear cluster-based 3D metal–organic frameworks with a good magnetocaloric effect

Abstract

Two coordination polymers [Ln₇(IDA)₃(HCOO)₃(μ₃-OH)₈(H₂O)₆]Cl₄·8H₂O (Ln = Gd, Dy; IDA⁻ = iminodiacetic anion) featuring a three-dimensional (3D) framework based on Ln₇ units were synthesized. According to X-ray structural analysis, the two compounds are isostructural; both consist of a garland-shaped Ln₇ building unit with a zigzag arrangement along the c-axis and one-dimensional round channels inside. Magnetic investigations demonstrate that 1Gd shows a good MCE with −ΔS_m^max = 40.85 J kg⁻¹ K⁻¹ at 3 K and ΔH = 7 T due to the larger mass ratio (metal/ligand) and increased magnetic density of the 3D structure.