Water-Stable Carborane-Based Eu 3+ /Tb 3+ 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, 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 m CB-Eu y Tb 1- y ( y = 0-1) MOFs using a highly hydrophobic ligand m CBL1: 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 Tb 3+ to Eu 3+ , and time-dependent emission of the series of mixed-metal m CB-Eu y Tb 1- y MOFs are reported. An outstanding increase in the quantum yield (QY) of 239% of m CB-Eu (20.5%) in the mixed m CB-Eu 0.1 Tb 0.9 (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.