Zn(ii)/Cd(ii) based mixed ligand coordination polymers as fluorosensors for aqueous phase detection of hazardous pollutants

Abstract

Environmental remediation, particularly in the context of water pollution, has been at the centre of a range of research domains over the past few decades. Metal organic frameworks (MOFs) or coordination polymers (CPs) are a relatively new class of infinite materials comprising metal nodes and linkers as repeat units. Exclusive merits of these materials such as tuneable porosity, and physical and chemical properties reflect in their extensive applications in fields such as sensing, adsorption, separation, catalysis, etc. In the present study, we evaluate the application of Zn(II)/Cd(II) based mixed ligand luminescent MOFs/CPs towards addressing the concerns related to water pollution. Firstly, the origin of photoluminescence in MOFs/CPs is discussed, which underlines the merits of Zn(II) and Cd(II) metal ions, mixed linker systems as well as the delicate host–guest interactions between the framework and analyte. The hydrolytic and chemical stability of the luminescent MOFs/CPs is prerequisite for their in-field sensing applications, which are critically studied in the context of Cd(II)/Zn(II) and mixed linker based luminescent MOFs/CPs. Subsequent sections separately underscore the important studies on sensing of organic pollutants viz., nitroaromatics, acetone, acetylacetone and paraquat as well as inorganic pollutants including di- and trivalent metal cations viz, Hg²⁺, Cu²⁺, Pb²⁺, Pd²⁺, Al³⁺, Fe³⁺ and Cr³⁺; and inorganic anions such as cyanide, iodide, chromate, dichromate, manganate etc. Efforts to develop paper strip based versatile sensors for noxious ions are also highlighted.