pH-Responsive Fluorescent Metal–Organic Framework as a Functional Nanofiller for Smart Coatings

Abstract

A zirconium-based UiO-type UiO-66-(OH) 2 metal−organic framework@carbon dot composite (Zr-MOF@ CD) is synthesized through a facile solvent-free thermal method. The Zr-MOF@CD exhibits pH-responsive fluorescence behavior, which emits blue fluorescence for pH < 9 at an emission wavelength of 470 nm. At pH > 9, the fluorescence color turns from blue to yellow, with the emission behavior at 535 nm. Zr-MOF@CDs can serve as functional nanofillers in the epoxy coating for the fabrication of a smart coating, which can realize coating damage warning and metal corrosion reporting. The blue fluorescence can be observed in the area of coating damage with just a minor scratch. Once the scratch is severe enough to expose the metal substrate, the cathodic reaction of oxygen reduction in the corrosion galvanic cell causes an increased pH, where the emission of yellow fluorescence can be identified. The stable fluorescence response is free from the influence of concentration, time, temperature, and the interfering substance. Zr-MOF@CDs can also serve as nanocontainers for loading with the corrosion inhibitor and realizing the repairing of metal corrosion. The development of the smart coating with dual functions of autonomous reporting and repairing holds great potential to improve the lifetime of metals in various industrial applications.

Selective Determination of HOCl in Environmental Water Samples and Real-Time Detection of HOCl Levels in Live Cells via Ratio Fluorescence Imaging Based on Eu3+-Modified and Carbon Dot-Encapsulated Metal Organic Frameworks

“…17 The UiO-66 as a typical representative of Zr-MOFs, has distinctive advantages such as highly chemical stability and unique pore structures that are easily modified with the functional groups (−NH 2 , −COOH, etc.). 18 It can be served as a platform role to bind different fluorescent substances including organic dye molecules and quantum dots to fabricate dual-emission chemosensors. 19 Lanthanide metal organic frameworks have been extensively developed as the fluorescent probes owing to their excellent optical properties, and the abundant carboxyl groups on the surface of UiO-66-(COOH) 2 that can coordinate with lanthanide ions such as Eu 3+ , Tb 3+ , and Ce 3+ to exhibit characteristic luminescence via the antenna effect.…”

“…The UiO-66 as a typical representative of Zr-MOFs, has distinctive advantages such as highly chemical stability and unique pore structures that are easily modified with the functional groups (−NH 2 , −COOH, etc.) . It can be served as a platform role to bind different fluorescent substances including organic dye molecules and quantum dots to fabricate dual-emission chemosensors .…”