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The investigation of dihydrazone Schiff base ligands as potential and appropriate chemosensors for fast, simple and portable detection of Cd(II) ion is reported. [Display omitted] • Dihydrazone Schiff bases – chemosensors for Cd(II) ion. • Photoluminescence on/off effect upon coordination of Schiff bases with Cd(II). • Fluorescence of ligands is enhanced when Cd(II) is added to test paper strips. Finding suitable probes for the rapid and sensitive detection of highly toxic pollutants is an urgent challenge for our environment. In this paper, three Schiff base ligands (H 2 L1 = 2 , 6-diacetylpyridine bis(isonicotinoylhydrazone), H 2 L2 = 2 , 6-diacetylpyridine bis(nicotinoylhydrazone) and H 2 L3 = 2 , 6-diacetylpyridine bis(picolinoylhydrazone)) have been used as potential chemosensors for Cd2+ detection. The corresponding Cd(II) complexes were prepared and it was found that the chemosensors coordinate similarly to the Cd2+ ion, eventually exhibiting different photoluminescent responses. Coordination of H 2 L1 and H 2 L2 to the Cd(II) ion results in a "turn-off" photoluminescence, while coordination of H 2 L3 show an excellent example of a "turn-on" mode of photoluminescence. Moreover, all three studied ligands are appropriate candidates for a fast, simple and portable method of Cd(II) ion detection. [ABSTRACT FROM AUTHOR]

A two-dimensional copper-based metal–organic framework: [Cu·(HL)·(DMF)] n (1). Its adsorption of Cd2+ is a process of quasi first-order kinetics, △G<0, and △H<0. The inorganic anions can alter the existing form of Cd2+, thereby affecting adsorption performance. [Display omitted] • A two-dimensional copper based metal organic framework was synthesized that could efficiently adsorbed Cd2+. • The thermodynamic analysis of adsorption shows that △G < 0 and △H < 0 during the adsorption of Cd2+. • The presence of inorganic ions changes the existing form of Cd2+, thereby affecting the performance of the adsorbent in adsorbing Cd2+. Metal-organic frameworks exhibit strong adsorption performance for Cd2+ in wastewater due to their multi-level pores and easily modified structure. In this paper, a copper based metal–organic framework: [Cu·(HL)·(DMF)] n (1) (H 3 L = 5-hydroxy isophthalic acid; DMF = N,N-dimethylformamide), was synthesized by hydrothermal synthesis method. The structural analysis shows that each Cu(II) in 1 is coordinated with four carboxylate O atoms from HL2− and one O atom from DMF. The two carboxylate groups in HL2− take μ 2 -η1:η1 to bridge two Cu(II) ions formed a two-dimensional structure. The scanning electron microscope (SEM) analysis shows that the nanomaterials prepared by the crushing method have dendritic structures and particle diameters of approximately 100 nm. The experimental results of the nano adsorbent adsorbing Cd2+ show that at an isoelectric point pH = 6, the optimal adsorbent concentration is 0.20 g/L. The maximum adsorption capacity at this time is 75.22 mg/g, which is superior to most MOFs adsorbents. At this optimal adsorbent concentration, as the solution pH increases, the adsorption capacity of the adsorbent for Cd2+ significantly increases. The thermodynamic analysis results of adsorption show that the △G < 0 and △H < 0 of the adsorbent in the range of 20–40 ℃, indicating that the adsorption of Cd2+ by the adsorbent is a spontaneous and exothermic process. The inorganic anions Cl−, HCO 3 −, NO 3 −, SO 4 2− inhibit the adsorption of Cd2+ by nano adsorbent at a pH of 6. However, at low pH values (4, 5), it promotes the adsorption of Cd2+. This is mainly because the presence of inorganic anions changes the form of Cd2+ in solution, affecting the adsorption of it by the adsorbent. [ABSTRACT FROM AUTHOR]