Highly stable rare earth metal-organic frameworks for proton conduction and magnetic refrigeration

Abstract

Four isomorphic rare earth metal-organic frameworks designated as {[(CH3)2NH2]0.7[RE2(BTDBA)1.5(lac)0.7(H2O)2]·solvent}n (RE = Tb (JXUST-19), Eu (JXUST-29), Gd (JXUST-42), and Dy (JXUST-43), where JXUST denotes Jiangxi University of Science and Technology) have been synthesized derived from a benzothiadiazole tetracarboxylate ligand (4′,4'''-(benzo[c][1,2,5]thiadiazole-4,7-diyl)bis([1,1′-biphenyl]-3,5-dicarboxylic acid), H4BTDBA). They present chain-based three-dimensional structures with one-dimensional channels extending along the b-axis. Notably, the free [(CH3)2NH2]+ cations within the channels serve as proton carriers during proton conduction. All complexes demonstrate significant proton conductivity dependent on relative humidity and temperature. Among them, JXUST-43 displays the peak conductivity achieved 7. 38 × 10–5 S·cm-1. In terms of magnetic research, JXUST-42 exhibits potential as a magnetorefrigerant, reaching a maximum entropy change (-ΔSmmax) of 16.63 J kg-1 K-1 at 3.5 K with ΔH = 7 T. And the presence of field-induced slow magnetic relaxation behavior with antiferromagnetic coupling is observed in JXUST-43.