Water-Stable Carborane-Based Eu3+/Tb3+Metal-Organic Frameworks for Tunable Time-Dependent Emission Color and Their Application in Anticounterfeiting Bar-Coding

: 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, LnMOFs 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-closododecaborane. 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 mCBEu0.1Tb0.9 (69.2%) is achieved, along with an increased and tunable lifetime luminescence (from about 0.5 to 10 000 mu s), 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.

Automated summary

In this study, we design and synthesize a series of water-stable and temperature-stable mCB-EuyTb1-y MOFs and report the tunable emission, energy transfer, and time-dependent emission of these materials. The quantum yield is significantly increased and the lifetime luminescence is enhanced and tunable, achieved by a highly effective energy transfer process. The time-dependent emission and high quantum yield provide a simple method for designing high-security anticounterfeiting materials.