3D oxalato-bridged lanthanide(<scp>iii</scp>) MOFs with magnetocaloric, magnetic and photoluminescence properties

Abstract

Four isostructural 3D lanthanide(iii) metal-organic frameworks with the general formula (H₆edte)_0.5[Ln^III(ox)₂(H₂O)] (Ln = Gd (1), Tb (2), Dy (3) and Ho (4); H₄edte = N,N,N',N'-tetrakis(2-hydroxyethyl)ethylenediamine) and ox = oxalate have been synthesized from oxalate. These compounds were characterized using single-crystal X-ray diffraction, FTIR and TGA/DTG. The magnetic investigation has been performed for 1-4 and the results reveal that a Gd(iii) containing MOF has the highest magnetic density and exhibits a larger cryogenic magnetocaloric effect (ΔS_m = 35.9 J kg^-1 K^-1 for ΔH = 9 T at 2.0 K) with a high Debye temperature (θ_D = 342(3) and r_D = 35). For the Dy derivative, an ac-out-of-phase signal was found, and further measurements under an applied field of 1000 Oe showed frequency-dependent out-of-phase magnetic susceptibility. Solid-state luminescence indicates that Tb and Dy-containing complexes are photoluminescent materials.