Pore-coordination sphere facilitated ratiometric fluorescent detection of organic amines in a substitutional metal–organic matrix†

Abstract

Multivariate metal–organic frameworks (MTV-MOFs) demonstrate strong potential as self-calibrating fluorescent sensors with desirable features of high stability and reliability due to the incorporation of multiple emissive centers and diverse functionality into a single material. In this work, a ligand substitutional metal–organic matrix HIAM-3001-PNT-25% with a ratiometric dual-emissive fluorescence response toward ammonia and aliphatic amines is designed and constructed. HIAM-3001-PNT-25% exhibits a sensitive fluorescence response toward ammonia and aliphatic amines in aqueous solutions, with a detection limit towards ammonia of 0.299 ppm. Furthermore, the influence from the pore-coordination sphere induced by hydrogen bonding interaction is analyzed systematically through fluorescence titration measurements, DFT calculations and an independent gradient model based on Hirshfeld partition analysis, which has offered helpful interpretation to the observed sensing behavior. The doping system demonstrates heightened sensitivity to cadaverine and can be fabricated into pliable films, which can be utilized as an indicator of meat freshness. This work reveals the crucial roles of the electron acceptor moiety on pore-coordination interaction and brings prospects for the development of efficient amine monitoring systems.