A post-modified lanthanide metal-organic frameworks as ratiometric luminescent sensor for the visual detection of 5-hydroxytryptamine.

5-Hydroxytryptamine (5-HT), a key neurotransmitter, is an important biomarker for carcinoid syndrome. We herein construct a ratiometric luminescent sensor by covalently coupling fluorescein 5-isothiocyanate (FITC) with lanthanide metal-organic frameworks (Ln-MOFs). In the presence of 5-HT, the emission of FITC increases while the emission of Eu decreases, accompanied by a distinct color change of emission from orange to green.