Phenylcarboxyl-terpyridine Based Metal-organic Gels For Anions Recognition And Dye Adsorption

Metal-organic gels?MOG?are formed by metal ions and organic ligands through the coordination,hydrogen bonding,?-?stacking,van der Waals force and so on.Due to its compositional characteristics,MOG possesses redox,magnetic,optical,chirality and thixotropy properties.In addition,as a metal-organic hybrid material,MOG usually could be prepared in a simple way and mild condition.Based on these characteristics,as an ideal intelligent soft material,MOG has a wide range of applications in drug delivery,catalysis,chemical sensing and adsorption.In this paper,a variety of metal organic gels were prepared based on the ligand carboxyphenyl-terpyridines,and further applied to anions recognition and methyl orange adsorption in water.?1?Tb-ContainingMetal-OrganicGelbasedonligand carboxyphenyl-terpyridines for Visual Sensing of Nitrite Under mild conditions?25^oC?,Tb-containing metal organic gel?Tb-MOG?with green fluorescence was prepared via simple mixing of the ligand 4-[2,2':6',2”-terpyridine]-4'-ylbenzoic acid?Hcptpy?and the central metal ion Tb³⁺.The synthesized Tb-MOG shows good mechanical reversibility,thermal stability and a certain degree of acid or alkali tolerance.Moreover,the Tb-MOG shows a specific response to NO₂^-based on the energy transfer between central metal ions(Tb³⁺)of Tb-MOG and NO₂^-.Thus,the fluorescent sensing system for NO₂^-was established with good selectivity and applied in analysis of NO₂^-in drinking water with satisfactory recovery rate.Test papers containing Tb-MOG were also prepared,and further realised the selective visual recognition of NO₂^-,which makes the Tb-MOG as a sensor more adaptive to practical application.?2?Carboxyphenyl-terpyridine-based a series of gels for visual recognition of multi-anions in a step-by-step way Gels as a soft recognition unit with stimuli-responsive characteristic have attracted increasing interest in anion sensing.However,developing gel-based sensors with simple synthesis methods and capable of selective multianalyte sensing is still a challenge.Herein,the polydentate ligand 4-[2,2':6',2”-terpyridine]-4'-ylbenzoic acid?Hcptpy?with multiple coordination sites was used for preparing gels and recognizing multi-anions.Interestingly,the Hcptpy alone without metal ions self-assembled to gels via only introducing of H₂PO₄^-or Cr₂O₇^2-which achieved the selective recognition of H₂PO₄^-and Cr₂O₇^2-with the white and yellow gels formation respectively.In addition to formation of gels with Zn²⁺,Al³⁺and Tb³⁺,respectively,Hcptpy also forms MOGs with a range of other metal ions(Mg²⁺,Ba²⁺,Cr³⁺,Cu²⁺,Hg²⁺,Cd²⁺,Sm³⁺,Eu³⁺and Dy³⁺).These as prepared MOGs have response to multiple anions,in order to improve the selectivity for anoins recognition,the step-by-step identification system including Hcptpy itself,the fbricated Zn-MOG,Tb-MOG,Eu-MOG and Cd-MOG was constructed with combining previous work,for selective and visual identification I^-,CO₃^2-,PO₄^3-,SCN^-,F^-,Br^-,N₃^-,NO₂^-,H₂PO₄^-,Cr₂O₇^2-,HPO₄^2-and S^2-.?3?Al-containing metal organic gel as an effective adsorbent for Methyl orange adsorption In this section,Al-containing metal organic gel?Al-MOG?was prepared according to the previous report.This MOG has a positive charge and employed as an adsorbent for fast adsorption of negatively charged methyl orange dyes in water.We investigated the effect of initial pH value,initial concentration of dye and adsorption time on the adsorption of methyl orange?MO?with Al-MOG,and found that the amount of adsorption increases with the initial concentration of MO increasing.Besides,the study on adsorption kinetics and thermodynamics conducted,indicating that the adsorption process followed the pseudo-second-order equation and the adsorption isotherms fitted the Freundlich model.And with the temperature increasing,the amount of adsorption decreases,demonstrating that the adsorption process is an exothermic process.