Recent publication in Chemistry of Materials journal describing the use of Eu3+/Tb3+ MOF for tunable time-dependent emission color.
New publication in Chemistry of Materials journal entitled “Water-Stable Carborane-Based Eu3+/Tb3+ Metal-Organic Frameworks for Tunable Time-Dependent Emission Color and Their Application in Anticounterfeiting Bar-Coding“, authored by the PhD student Zhen Li (Institute of Materials Science of Barcelona, ICMAB-CSIC) as the first author. The paper results from a strong collaboration between the group of Dr. José Giner (Molecular and Supramolecular Materials – ICMAB-CSIC) and Nanosfun with the participation of our Senior Postdoctoral Researcher Dr. Claudio Roscini and our group leader Prof. Daniel Ruiz-Molina. Besides, the work had the contribution of Dr. Rosario Núñez (ICMAB-CSIC), Dr. Eliseo Ruiz (ICMAB-CSIC), Dr. Francesc Teixidor (ICMAB-CSIC), Dr. Clara Viñas (ICMAB-CSIC) and Dr. Mark E. Light (Department of Chemistry, University of Southampton, UK).
In this work, the authors reported the formation of optical-active MOF for their use in anticounterfeiting bar-coding. In this sense, the combination of MOFs with lanthanide (Ln) ions results in inherent optical properties, including high luminescence quantum yields, narrow and strong emission bands, large Stokes shifts, long luminescence lifetimes, and an emission wavelength undisturbed by the surrounding chemical environment. Their luminescence is associated with an energy transfer (ET) from the ligand, potentially engaging in a variety of applications, such as, e.g., sensors, optoelectronic and solid-state lighting devices, or bioimaging, among others. Of particular interest is the exploitation of emissive Ln-MOFs as optical markers for high-security anticounterfeiting technologies to prevent illegal copies of sensitive identity documents, banknotes, diplomas, and certificates. However, regardless of the great potential of these materials, to date, they have proved unsuitable for practical applications due to their limited chemical and/or optical stability under environmental conditions.
To overcome these limitations, the authors proposed the introduction of carborane clusters such as icosahedral carboranes 1,n-C2B10H12 (n = 2, 7 or 12), a class of commercially available and exceptionally stable three-dimensional (3D) aromatic boron-rich clusters that possess material-favorable properties such as thermal/chemical stability and high hydrophobicity.
ABSTRACT: Luminescent lanthanide metal–organic frameworks (Ln-MOFs) have been shown to exhibit relevant optical properties of interest for practical applications, though their implementation still remains a challenge. To be suitable for practical applications, Ln-MOFs must be not only water stable but also printable, easy to prepare, and produced in high yields. Herein, we design and synthesize a series of mCB-EuyTb1–y (y = 0–1) MOFs using a highly hydrophobic ligand mCBL1: 1,7-di(4-carboxyphenyl)-1,7-dicarba-closo-dodecaborane. The new materials are stable in water and at high temperature. Tunable emission from green to red, energy transfer (ET) from Tb3+ to Eu3+, and time-dependent emission of the series of mixed-metal mCB-EuyTb1–y MOFs are reported. An outstanding increase in the quantum yield (QY) of 239% of mCB-Eu (20.5%) in the mixed mCB-Eu0.1Tb0.9 (69.2%) is achieved, along with an increased and tunable lifetime luminescence (from about 0.5 to 10 000 μs), all of these promoted by a highly effective ET process. The observed time-dependent emission (and color), in addition to the high QY, provides a simple method for designing high-security anticounterfeiting materials. We report a convenient method to prepare mixed-metal Eu/Tb coordination polymers (CPs) that are printable from water inks for potential applications, among which anticounterfeiting and bar-coding have been selected as a proof-of-concept.
Funding: This work was financially supported by the MINECO (PID2019-106832RB-I00), MICINN through the Severo Ochoa Program for Centers of Excellence for the FUNFUTURE (CEX2019-000917-S, MDM-2017-0767, and SEV-2017-0706 projects), grant RTI2018-098027-B-C21 funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe and the Generalitat de Catalunya (2017/SGR/1720 and SGR2017-1289). Z.L. is enrolled in the UAB Ph.D. program and acknowledges the China Scholarship Council (CSC) for his Ph.D. grant (201808310071).