Dual-emission ratiometric fluorescent probe-based lanthanide-functionalized hydrogen-bonded organic framework for the visual detection of methylamine

Developing a highly sensitive and selective visualized sensor for volatile organic amines is a challenge in materials science. Here, we report a Eu3+-functionalized hydrogen-bonded organic framework (HOF) (named Eu@Tt-TPA) for the ratiometric fluorescence detection of methylamine (MA). The unbonded carboxyl group in the structure can bind Eu3+ with the skeleton to produce double emission, and can also produce hydrogen bonds with the analyte MA. Eu@Tt-TPA exhibits a dual emission, at 425 nm for the HOF and 615 nm for Eu3+, under excitation at 310 nm, realizing the visual ratiometric detection of MA in aqueous solution. The ratiometric sensing performs a self-calibration effect and reduces the background. Furthermore, a portable gas sensor was prepared by solidifying Eu@Tt-TPA into a hydrogel using the sodium salt of hydroxymethyl cellulose. When exposed to MA vapor, this hydrogel-based sensor exhibits a distinct color change, which varied with the MA concentration. Thus, the dual emission ratiometric fluorescent probe Eu@Tt-TPA, for the simultaneous detection of MA liquid and vapor with high selectivity and sensitivity, a low detection limit (0.87 ppm) and recoverability, was achieved and investigated for use in wastewater.

Automated summary

A Eu3+-functionalized hydrogen-bonded organic framework (HOF) named Eu@Tt-TPA was developed for ratiometric fluorescence detection of methylamine (MA) with high sensitivity and selectivity. The dual emission property of the material enables visual ratio detection of MA in aqueous solution and solidified into a hydrogel sensor for distinct color change response to MA vapor concentration, suitable for wastewater treatment applications.