Ratiometric Fluorescent Chemosensor for Zn ²⁺ Ions in Environmental Samples Using Supermicroporous Organic‐Inorganic Structures as Potential Platforms

Abstract

Abstract We report the fabrication of supermicroporous, fluorometric chemosensors with a Zr‐metal–organic framework as carrier. The fabricated ratiometric fluorescent chemosensors (RFCs) were suitable for the selective and sensitive fluorometric recognition of ultra‐trace concentrations of heavy metals, such as Zn 2+ ions, in water sources. The RFCs were designed by performing direct pressure‐assisted immobilization of a hydrophobic organic probe inside supermicroporous cubic Zr‐MOFs. The immobilized organic probe exhibited high sensitivity and selectivity toward Zn 2+ in a uniform super‐microchannel pore, long‐range intergrowing crystal structures. Ratiometric fluorometric sensing assay of the Zn 2+ ions revealed the high selectivity of the ions in a mixture of multiple interfering ions. This phenomenon was due to the structure of the RFCs, the pH of the system, the composition of the competitive ion system, and the Zn‐to‐RFCs binding process, which occurred via electron transfer. The RFCs exhibited a wide detection and monitoring range for Zn 2+ ions. The lower limit of detection was 0.16 ppb, and a fast response within seconds was observed during complexation with the Zn 2+ ion target. The surface functionality and long‐term stability of RFCs enable the practical and multiple reuse/cycles of Zn 2+ ion recognition.