Pure and Mixed {Nd/Yb} Carborane-based Metal-Organic Frameworks integrating Slow Magnetic Relaxation, Magnetocaloric Effect and NIR emission

Abstract

Multi-lanthanide metal-organic frameworks (MOFs) provide a versatile platform for designing materials with tailored multifunctional properties. Here, we report the synthesis and full characterization of novel carborane-based MOFs of formula {[(Nd_yYb_1-y)₃ (mCB-L)₄ (NO₃)(DMF)_x] _n •Solv}, including homometallic Nd (y = 1), Yb (y = 0) compounds and the mixed Nd/Yb analogue (y = 0.44). Magneto-thermal and optical properties were investigated using dc and ac Magnetometry, X-ray Absorption Spectroscopy (XAS), X-ray Magnetic Circular Dichroism (XMCD), and Luminescence measurements. The two Kramers ions, Nd³⁺ and Yb³⁺, yield multifunctional MOFs combining slow relaxation of the magnetization (U/k B ~ 19 K), magnetocaloric effects (-ΔSm ~ 1.6 R at 5 T, 1.8 K) and near-infrared (NIR) luminescence. In particular, the mixed Nd/Yb MOF exhibits NIR emission at 998 nm and 1060 nm arising from partial Nd → Yb energy transfer. Our findings illustrate how carborane-based ligands can engineer multi-lanthanide frameworks with tailored properties, highlighting the potential of {Nd/Yb} MOFs as multifunctional materials for quantum technologies, optical communication, and cryogenic cooling.