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A new molecular Gd-based 2D metal-organic-framework opens new frontiers to on-surface magnetic cooling of technological devices

The new edition of the Journal of Materials Chemistry A portrays in its cover a novel on-surface deposited Gd 2D metal-organic framework (MOF), investigated by an international research team led by Carolina Sañudo (UB) and Elena Bartolomé (ICMAB-CSIC). The team comprises people from the Institute of Theoretical and Computational Chemistry of the UB (IQTCUB), the Institute of Nanoscience and Materials of Aragon (INMA/CSIC/UNIZAR), the National High Magnetic Field Laboratory (United States) and the University of Oxford (United Kingdom).

Anna Drou
Anna Drou
04 April 2024
COVER. The cover displays [Gd(MeCOO)(PhCOO)2], a new Gd-based 2D MOF synthesized and characterized by E. Bartolomé (ICMAB-CSIC), C. Sañudo (UB) et al. The material shows magnetocaloric effect both in bulk and chemisorbed on a Silicon substrate, opening up the possibilities for on-surface cooling devices.
COVER. The cover displays [Gd(MeCOO)(PhCOO)2], a new Gd-based 2D MOF synthesized and characterized by E. Bartolomé (ICMAB-CSIC), C. Sañudo (UB) et al. The material shows magnetocaloric effect both in bulk and chemisorbed on a Silicon substrate, opening up the possibilities for on-surface cooling devices.

Lanthanide-based MOFs stand out as a versatile class of molecular compounds featuring appealing magnetic, electrical and optical properties for a broad range of applications. In particular, two-dimensional (2D) molecular compounds provide an exceptional playground for designing planar materials, heterostructures and multifunctional devices.

“The investigation of such multifunctional metal-organic compounds involves a multidisciplinary approach, where the characterization of the materials through an array of techniques including dc/ac magnetometry, calorimetry, luminescence and X-ray magnetic circular dichroism is crucial”, emphasizes Elena Bartolomé, tenured scientist at the Department of Smart Molecular Inorganic and Hybrid Materials at ICMAB-CSIC.

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Figure 1. (Top, left) Crystal structure of the new 2D MOF, [Gd(MeCOO)(PhCOO)2]: crystal packing along the a-axis shows three layers separated only by Van der Vaals interactions; (Top, right) Imaginary component of the ac susceptibility as a function of the frequency, c’’(f), of the powdered compound at 0.2 T and different temperatures ranging from 1.8 K to 20 K, showing slow magnetic relaxation through different mechanisms; (Bottom) Magnetic entropy change, -DSm, for Gd 2D MOF1 grafted on a TSP functionalized Si wafer, with the wafer parallel (left) and perpendicular (right) to the applied magnetic field. 

 

In their study, the team has prepared and fully characterized a new 2D MOF based on gadolinium (Gd), a chemical element of the rare earth group that has seven unpaired electrons and can act as a magnetic coolant at extremely low temperatures.

In this compound, each Gd(III) ion behaves as if it were a magnet molecule (single molecule magnet, SMM). Because it is a 2D reticular compound, each monolayer forms an ordered array of SMMs. SMMs offer promising prospects for information storage, where each Gd(III) acts as bit. In addition, owing to the presence of Gd(III), the compound exhibits a high magnetic entropy and magnetocaloric effect (MCE).

“This MOF is special, as it is two-dimensional. 2D MOFs are metal-organic equivalents to graphene, and like this compound, they can be exfoliated into monolayers or aggregates of few monolayers on the nanometric scale,” says Carolina Sañudo, professor at the Department of Inorganic and Organic Chemistry of the UB.

In the article, the team has achieved the growth of nanocrystals of the compound in a semiconductor silicon surface, a decisive step to be able to use molecular materials in devices for technological applications. In the field of magnetic cooling, nanocrystals deposited on the semiconductor can be used as surface coolants at cryogenic temperatures, a property of interest to lower the temperature inside circuits or electronic devices.

The conclusions of the new study indicate that it is possible to use gadolinium compounds for magnetic cooling in devices, not only by being able to nanostructure the material on a semiconductor, but showing that the magnetocaloric effect is maintained at the nanoscale and the new compound can function as a magnetic coolant on the surface.

 

Original article: Kumar, S., Gabarró-Riera, G., Arauzo, A. Hrubý, J., Hill, S., Bogani, L., Rubio-Zuazo, J., Jover, J., Bartolomé, E.*, Sañudo, C.* (2024) «On-surface magnetocaloric effect for a van derWaals Gd(III) 2D MOF grown on Si». Journal of Materials Chemistry A. 12(11), 6269-6279.

 

Adapted from UB press relase: https://web.ub.edu/web/actualitat/w/nou-compost-molecular-amb-aplicacions-tecnologiques-nanoescala

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