Metal Ion Sensing and Electrochemical Behavior of MOF Derived ZnCo2O4

• Published in: European journal of inorganic chemistry 2019-07, Vol.2019 (26), p.3076-3083
• Main Authors: Ghosh, Debamalya, Pal, Ananya, Ghosh, Susanta, Gayen, Arup, Seikh, Md. Motin, Mahata, Partha
• Format: Article
• Language: English
• Subjects: Aqueous solutions; Cobalt; Copper; Detection; Electrochemical analysis; Flux density; Foreign exchange rates; Inorganic chemistry; Ions; Ligands; Luminescence; Luminescence quenching; Mapping; Mercury (metal); Metal ions; Metal-organic frameworks; Purity; Pyridine dicarboxylate; Sensors; Synthesis; X-ray diffraction; Zinc
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201900439

A metal‐organic framework (MOF) with the formula {(H2pip)[Zn1/3Co2/3(pydc‐2,5)2(H2O)]·2H2O}{where H2pip = piperazinediium, pydc‐2,5 = pyridine‐2,5‐dicarboxylate}, 1, has been synthesized. To confirm the structure and phase purity of 1, the PXRD pattern of the synthesized compound has been compared with the simulated PXRD pattern generated from the single‐crystal X‐ray data of isomorphous pure Co compound synthesized by Niu and Co‐workers. Upon solid state annealing of the mixed‐metal precursor (MOF) at 400 °C for one hour, pure ZnCo2O4 was obtained. The phase purity of ZnCo2O4 was confirmed by powder X‐ray diffraction. The as obtained ZnCo2O4 was fully characterized using PXRD, SEM, TEM, and EDX elemental mapping analysis. The particle size is in the range of 22 nm‐40 nm with a dominant size of 30 nm. The emissive properties of nano‐sized ZnCo2O4 at 391 nm upon excitation at 310 nm have been probed for the luminescence‐based sensing of metal cations in aqueous medium. The metal ion sensing is based on the differential change in intensity, which in turn reflects the strength of the interaction between ZnCo2O4 and the metal ion. Such interactions can be rationalized within the framework of the ligand exchange rate as well as ionic radii of the aquated metal ions. Accordingly, Cu2+ and Hg2+ with highest ligand exchange rate exhibit maximum luminescence quenching, 71.7 % and 51 %, respectively. On the other hand, the nanostructured ZnCo2O4 also shows super capacitance behavior with a maximum energy density of 2.39 Wh kg–1 at a power density of 36.66 W kg–1. A mixed metal MOF Precursor has been synthesized and on solid state annealing of the precursor pure nano‐sized ZnCo2O4 was obtained. The emissive property of the nano‐sized ZnCo2O4 has been probed for the luminescence‐based sensing of metal cations in the aqueous medium. The nanostructured ZnCo2O4 also shows super capacitance behavior.