C2O42−-templated cage-shaped Ln28 (Ln = Gd, Eu) nanoclusters with magnetocaloric effect and luminescence

Abstract

The assembly of high-nuclearity lanthanide nanoclusters with favourable magnetocaloric effects suffers from a significant challenge. Herein, two outstanding examples of cage-shaped nanoclusters, namely, [Ln₂₈(IN)₂₅(C₂O₄)₆(HCOO)(μ₃-OH)₃₆(μ₂-OH)₂(H₂O)₃₆]·8Br·xH₂O (Ln = Gd and Eu; x = 21, abbreviated as Gd₂₈; x = 17, abbreviated as Eu₂₈, HIN = isonicotinic acid; H₂C₂O₄ = oxalic acid) have been triumphantly designed and constructed under hydrothermal conditions. The crystallographic study revealed that the aesthetically pleasing triangle-shaped Gd₁₂ subunit and Gd₁₆ subunit built separately from four Gd₃ units and four Gd₄ units, respectively, are shaped into an unprecedented cage-shaped configuration. Prominently, six small and simple C₂O₄²⁻ anions generated via the in situ reaction of HIN are faultlessly anchored in the cage-shaped framework. Furthermore, the existence of abundant Gd^III ions impart Gd₂₈ with a captivating magnetic entropy change (−ΔS^max_m = 37.5 J kg⁻¹ K⁻¹) at 2.0 K for ΔH = 7.0 T.