Densely Packed Lanthanide Cubane Based 3D Metal–Organic Frameworks for Efficient Magnetic Refrigeration and Slow Magnetic Relaxation

Abstract

Two isostructural densely packed squarato-bridged lanthanide-based 3D metal-organic frameworks (MOFs) [Ln5(μ3-OH)5(μ3-O)(CO3)2(HCO2)2(C4O4)(H2O)2] [Ln = Gd (1) and Dy (2)] show giant cryogenic magnetic refrigeration (for 1) and slow magnetic relaxation (for 2). The structural analyses reveal the presence of a self-assembled crown-shaped building unit with a cubane-based rectangular moiety that leads to a special array of metal centers in 3D space in the complexes. Magnetic investigations confirm that complex 1 exhibits one of the largest cryogenic magnetocaloric effects among the molecular magnetic refrigerant materials reported so far (-ΔSm = 64.0 J kg(-1) K(-1) for ΔH = 9 T at 3 K). The cryogenic cooling effect (of 1) is also quite comparable with that of the commercially used magnetic refrigerant gadolinium-gallium garnet, whereas for complex 2, slow relaxation of magnetization was observed below 10 K.

Coordination‐Cluster‐Based Molecular Magnetic Refrigerants

“…In 2016, Konar et al synthesized two isostructural densely packed squarato‐bridged Ln 5 ‐cluster‐based 3D frameworks,66 73a (Figure ) and 73b . The Ln cubanes are arranged in a distorted tetrahedral manner, and two adjacent tetrahedra are connected through a corner‐sharing triangular plane; the plane shares the remaining corner with another adjacent plane to give the 2D layer, which is further bridged by HCOO – groups and H 4 sq ligands to generate the 3D frameworks.…”

“…Compared with discrete 4f‐metal‐cluster‐based molecular magnetic refrigerants,39–50 the numbers and types of pure 4f‐metal‐cluster‐based extended structures serving as molecular magnetic refrigerants are greater (Table );51–67 this may be because Ln ions possess various coordinated geometries and high coordination numbers, as well as minimal stereochemical preferences.…”

“…Since then, a series of pure 4f‐metal‐based 3D frameworks serving as molecular magnetic refrigerants have been reported,25,27,58–67 and the record for the –Δ S m value is frequently broken. Nonetheless, most of them (CPs 1a , 1b , and 59 – 67 ) are constructed from {Gd 2 } dimers or inorganic Gd–OH chains and carboxylate ligands,25,58–62 so high‐nuclearity pure Gd cluster based 3D CPs are rarely documented 63–67…”

Magnetic Behavior of Luminescent Dinuclear Dysprosium and Terbium Complexes Derived from Phenoxyacetic Acid and 2,2’-Bipyridine

“…It has been claimed that this special class of materials could be explored in terms of several potential applications, such as high-density data storage, quantum computing, molecular spintronics, cryogenic magnetic refrigeration, fabrication of nanoscopic molecular devices, etc. [1][2][3][4][5][6]. The rich quantum effect of SMMs leads to tunneling of magnetization, quantum coherence, or quantum superposition at a molecular level.…”

Synthesis, crystal structures and magnetic properties of two heterometallic {Ln8Cr4} (Ln = Gd3+ and Tb3+) complexes with one-dimensional wave chain structure

“…On top of this, the magnetic entropy change of DS m can attain 23.40 J kg À1 K À1 (44.90 mJ cm À3 K À1 ) at about 3 K and DH ¼ 7 T.Besides, fluorescence measurements of {Tb 8 Cr 4 } display typical characteristic Tb-based luminescence.Based on the above considerations, 3d-Gd metal clusters can be a good candidate to trigger a large MCE. 18,19 By introducing 3d metal ions into lanthanide clusters can not only exhibit a more superior nature, but also have a broad application prospect in elds, including light, electricity, magnetism and catalysis. 9,10 At present, more and more 3d-Gd metal clusters with large MCE have been prepared, ranging from molecular clusters to multi-dimensional coordination polymers where the maximum ÀDS m attains 42.8 J kg À1 K À1 at 3 K for DH ¼ 7 T. 20-26 Among plentiful 3d ions, Cr 3+ ions, closing to isotropic, makes them a good selection as a raw material for magnetic refrigerants.…”