Tuesday, 09 January 2024
Multifunctional rare-earth materials à la carte: A novel synthesis approach
Researchers from various Spanish institutes, including the ICN2, have developed a novel synthesis technique for the generation of multi-metallic rare earth metal-organic frameworks (MTV RE MOFs). The pioneering approach used by the authors of this study, published in ‘Advanced Functional Materials’ and featured on its back cover, opens pathways for tailoring combinations of these ions to design materials with specific and diverse applications.
Among the variety of techniques devised by scientists to design new materials with custom characteristics is the strategic incorporation of multiple metal elements in complex chemical structures, such as the metal-organic frameworks (MOFs). These are composite materials constructed by linking organic molecules with metal ions, forming periodic, extended architectures. The inclusion of diverse metallic elements in the framework, placed at equivalent sites in different parts of its periodic structure, leads to multi-metal multivariate (MTV) MOFs. These can exhibit new or enhanced photo-, electro-, calalytic, or luminescence properties.
Researchers are particularly interested in multi-metal materials based on rare-earth (RE) elements –which include the 15 lanthanides, scandium, and yttrium. Exceptional properties desirable for applications in energy conversion, catalysis, luminescence, and magnetism can be achieved thanks to the distinct electron configurations of these elements. However, the synthesis of rare-earth-based MOFs is still rather challenging, in particular when cations of different sizes are taken into account. So far only 2 or, at best, 3 different RE metals have been successfully incorporated into MOFs.
A study recently published in the journal Advanced Functional Materials and featured on the back cover of the journal reports on a novel synthesis method that enables the integration of two to eight rare-earth metal elements into a single structure. The authors –a team of researchers from the Institute of Materials Science of Barcelona (ICMAB-CSIC, Spain), the Nanostructured Functional Materials Group of the Catalan Institute of Nanoscience and Nanotechnology (ICN2, Spain), the University of Southampton (UK), the University of Zaragoza (Spain) and the ALBA Synchrotron (Spain)— were able to build multi-metallic multifunctional MOFs including metal cations of different species and sizes by appropriately choosing the linkers and the initial molar ratio of the metal elements.
The effectiveness of this innovative approach was proved by a significant milestone: the synthesis of the first-ever MOF incorporating eight different rare earth cations (La, Ce, Eu, Gd, Tb, Dy, Y, and Yb) uniformly distributed within the network. In addition to this structure, named mCB-8RE, the scientists also built the corresponding MTV MOFs containing two, four, and six RE cations, respectively. In doing so, they demonstrated a high degree of control over the number and size of incorporated cations (obtained by modulating the intermetallic distances and other parameters of the reaction), as well as the ability to overcame compositional segregation hurdles during synthesis reported in previous works.
This remarkable study not only introduces a pioneering method to synthesise multi-metallic MTV MOFs based on rare-earth metals, but also sets the stage for investigating and crafting multifunctional materials with tailored magnetic, optical, and thermal characteristics. These materials can find applications in many technological fields: in particular, they can offer new solutions for computer memories, for luminescent systems (used in anticounterfeiting and more), and even for quantum computing. In fact, this strategy could be utilised to develop "QuMOFs" (qubits MOFs), where a large number of qubits are allocated within these structures.
Reference article:
Zhen Li, Xiao-Bao Li, Mark E. Light, Anna E. Carrillo, Ana Arauzo, Manuel Valvidares, Claudio Roscini, Francesc Teixidor, Clara Viñas, Felipe Gándara, Elena Bartolomé, José Giner Planas, A Metal-Organic Framework Incorporating Eight Different Size Rare-Earth Metal Elements: Toward Multifunctionality À La Carte. Advanced Functional Materials, Volume 33, Issue 47, 2023 -2307369. DOI: 10.1002/adfm.202307369