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Nitro compounds are widely used in modern industries. Among them, 2, 4-dinitrophenylhydrazine (DNH) is extremely harmful. It is of great significance to develop methods for the detection of DNH. In this work, chitosan was used as the substrate material, and fluoroborondipyrrole (BODIPY) was used as the fluorophore. Chitosan was endowed with the fluorescence sensing ability by the introduction of BODIPY units. First, BODIPY derivatives (NO-3 and BO-1) with an alkynyl group (C≡C) were synthesized. Second, small molecules NO-4 and BO-2 with an aldehyde group (–CHO) were obtained. Finally, the –NH2 groups on chitosan underwent a click reaction (–NH2/C≡C) and a Schiff base formation reaction occurred (–NH2/–CHO) to form three polymer probes C1, C2 and C3. C＝C formed in the click reaction can interact with DNH and can be used as recognizing sites for DNH. These chitosan probes have good thermal stability and could selectively recognize DNH, showing notable fluorescence quenching effects, which are visible to the naked eye. DNH is a typical electron-deficient compound, and the polymer fluorescent probe contains electron-rich groups, which makes it easier for the two species to combine and cause fluorescence changes. C1 is flexibly cross-linked, C3 is rigidly cross-linked, and C2 has a non-crosslinked structure, and they show different rheological properties. This work expands the application of chitosan. [ABSTRACT FROM AUTHOR]

Mixed-ligand metal–organic frameworks (MOFs) are usually synthesized from two or more organic ligands as initial reactants, and MOFs synthesized from one organic ligand precursor through partial in situ reactions remain very limited. Herein, by introducing an imidazole-tetrazole bifunctional ligand, 5-(4-imidazol-1-yl-phenyl)-2H-tetrazole (HIPT), as a single ligand and performing in situ hydrolysis of the tetrazolium group, a mixed-ligand Co(II)-MOF based on HIPT and 4-imidazol-1-yl-benzoic acid (HIBA), [Co2(μ3-O)(IPT)(IBA)]·x solvent (Co-IPT-IBA), was constructed and applied to capture I2 and methyl iodide vapours. Single crystal structural analyses reveal that Co-IPT-IBA exhibits a 3D porous framework with 1D channels based on the relatively few reported ribbon-like rod SBUs. The nitrogen adsorption–desorption isotherms indicate that the BET surface area of Co-IPT-IBA is 168.5 m2 g−1 and it possesses both micropores and mesopores. Due to its porosity, nitrogen-rich conjugated aromatic rings, and Co(II) ions, Co-IPT-IBA was applied to capture iodine molecules in vapour and exhibited an adsorption capacity of 2.88 g g−1. By combining the IR, Raman, XPS and grand canonical Monte Carlo (GCMC) simulation results, it was deduced that the tetrazole ring, coordination water molecules, and the redox potential of Co3+/Co2+ facilitate iodine capture. The presence of mesopores was also responsible for the high iodine adsorption capacity. In addition, Co-IPT-IBA showed the ability to capture methyl iodide in vapours with a moderate capacity of 625 mg g−1. The transformation of crystalline Co-IPT-IBA to amorphous MOFs may be due to the methylation reaction. This work represents a relatively rare example of methyl iodide adsorption by MOFs. [ABSTRACT FROM AUTHOR]