C2O42--Templated [Ln2Ni] Heterometallic Compounds for Enhanced Magnetocaloric Effect at Low-Field

Abstract

In the history of magnetochemistry development, lanthanide-transition (3d-4f) heterometallic compounds have been considered an attractive candidate for magnetic refrigerant. Herein, a series of heterometallic compounds have been designed templated by C2O42- anions, that is, {[Ln2Ni(L)(C2O4)2(H2O)2]·H2O}n [Ln = GdIII (abbr. Gd2Ni), = SmIII (abbr. Sm2Ni), = TbIII (abbr. Tb2Ni), H2C2O4 = oxalic acid; H4L = ethylene diamine tetraacetic acid]. The structural analysis reveals that Ln2Ni compounds feature a C2O42--templated wavy-shaped two-dimensional layer. Then, adjacent wavy-shaped layers are further aggregated by C2O42– anions, resulting in an innovative three-dimensional metal-organic framework. Magnetization analysis revealed that Gd2Ni exhibits a favorable −ΔSmmax of 38.0 J kg-1 K-1 at 2.0 K for 7.0 T. Besides, the C2O42--templates anchored in the architecture display a decent magnetocaloric effect at low-field (−ΔSm = 25.1 J kg−1 K −1 at 2.0 T for 2.0 K and −ΔSm =14.5 J kg−1 K −1 at 1.0 T for 2.0 K), outperforming most 3d-4f heterometallic compounds reported previously.