A Highly Stable Framework of Crystalline Zinc Phosphite with Selective Removal, Recovery, and Turn‐On Sensing Abilities for Mercury Cations in Aqueous Solutions

Abstract

A highly stable framework of organic-inorganic hybrid zinc phosphite (NTOU-4) and its cobalt analogue (NTOU-4a) were synthesized under the hydro(solvo)thermal conditions and structurally characterized by single-crystal X-ray diffraction. Their frameworks consisted of inorganic metallophosphite chains, in which the metal atoms were interlinked through 1H-1,2,4-triazole-3,5-diamine and 1,4-benzenedicarboxylate linkers to form new crystalline materials. It is extremely difficult to achieve the consolidation of three distinct coordinations of metal-carboxylate, metal-triazolate, and metal-phosphite bonds into one crystal, resulting in the synthesis of the first mixed-ligand terephthalate-metallophosphite solids in the absence of organic molecules as templates or space-filling counters in their structures. Interestingly, the zinc compound not only exhibits high thermal stability (up to 400 °C in air) and chemical resistance to seawater, aqueous solutions (pH 3-11), and organic solvents at boiling conditions, but also shows selective removal, recovery, and "turn-on" sensing abilities of toxic mercury ions in aqueous solutions. Furthermore, the synthesis, characterization, and the difference of the framework stabilities between isostructural zinc and cobalt compounds are also reported.

An Unprecedented Interpenetrating Structure Built from Two Differently Bonded Frameworks: Synthesis, Characteristics, and Efficient Removal of Anionic Dyes from Aqueous Solutions

“…Attempts to synthesize an isostructural Co compound with NTOU‐5 were unsuccessful. The soft Lewis acid‐base pairs (nitrogen‐donor ligands prefer to bond with softer zinc ions) may cause this reaction: only the octahedral Zn sites of the anionic [Zn 2 (OX) 3 ] 2− frameworks are replaced by cobalt ions, whereas the Zn ions in the tetrahedral positions of cationic [Zn(TIMB)] 2+ networks remain intact, resulting in the formation of the interpenetrating analogue (pink crystals) with a different mixed‐metal composition.…”

“…[28] Attempts to synthesize an isostructural Co compound with NTOU-5 were unsuccessful. The soft Lewis acid-base pairs (nitrogen-donor ligandsp refer to bond with softer zinc ions) may cause this reaction: [29][30][31][32] only the octahedral Zn sites of the anionic [Zn 2 (OX) 3 ] 2À frameworks are replaced by cobalt ions, whereas the Zn ions in the tetrahedral positions of cationic [Zn(TIMB)] 2 + networks remain intact, resultingi nt he formation of the interpenetrating analogue (pink crystals) with ad ifferent mixed-metal composition.For now,o ne of the greatest environmental issues the world faces is the removalo fh armful pollutants that affect animals, plants, and human beings alike. [33,34] Among those pollutants, large numbers of organic dyes from industrial wastes have causeds erious environmental damage (about 140-7000 to f organic compounds are discharged into the aquatic system).…”

Magnetic/Polyetherimide-Acrylonitrile Composite Nanofibers for Nickel Ion Removal from Aqueous Solution

“…Inorganic NP adsorbents, such as metal oxides, carbon nanotubes, and polymeric nanoadsorbents, are suitable nanomaterials for removing heavy metals from an aqueous system because of their unique chemical and physical properties [ 20 , 21 , 22 , 23 , 24 , 25 ]. These NPs agglomerate easily due to their low solubility in aqueous mediums and are difficult to recycle.…”

Stable Crystalline Organic–Inorganic Hybrid Indium Phosphate with Dye Removal and Ractopamine Detection Applications

“…Even though great efforts have been devoted to the synthesis and design of stable crystalline materials via different synthetic strategies and methods, stable organic–inorganic hybrid solids are still limited. ,, From a structural perspective, the strong coordination bonds and steric hindrance around the metal centers are crucial to determining whether or not the compounds resist the attack and intrusion of guest molecules. Previous reports also indicate that stable crystalline structures could be synthesized by either using high-valent metal ions as central nodes, matching Pearson’s hard–soft acid–base principle, or introducing hydrophobic atoms/molecules for steric hindrance to block the metal centers; i.e., carboxylate- and azolate-based ligands work as hard and soft bases that form stable structures along with high-valent metal ions (Al 3+ , Fe 3+ , Cr 3+ , Ti 4+ , and Zr 4+ ) and softer divalent metal ions (Zn 2+ , Cu 2+ , Ni 2+ , and Mn 2+ ), respectively. ,− The stability of crystalline materials was enhanced through postsynthetic, fluoride, nonpolar alkyl-functionalized approaches . Considering these factors, a mixed strategy based on previous reports was applied for the synthesis of a new organic–inorganic hybrid metal phosphate.…”