Hydroxyl-Substituted Triazine-Based Cd-MOF Membrane-Based Materials with M–N Bond: Synthesis, Structure Characterization, and Fluorescence Sensing Applications

A 5-amino-2-hydroxybenzoic acid-modified triazine polycarboxylate metal–organic framework [Cd(ODTBBA)] 5DMF·3H2O (Compound 1) has been successfully designed and synthesized based on the triazine poly(carboxylic acid) ligand ODTBBA (5,5′-((6-oxo-1,6-dihydro-1,3,5-triazine-2,4-diyl)bis(azanediyl))bis(2-hydroxybenzoic acid)) and the transition metal source Cd(NO3)2·4H2O through the solvothermal method. Compound 1 featured a three-dimensional network structure constructed by the interconnection and interpenetration of Cd–O/N polyhedron and the ligand ODTBBA. Due to the instability of the compound in water and ethanol, we propose a new strategy of stabilizing metal organic frameworks using polymer materials; the complex was mixed into polyvinylidene fluoride for the preparation of Cd-MOF film material. The experimental results showed that the Cd-MOF film material with compound 1 has excellent metal framework stability and fluorescence properties. Therefore, we explored its fluorescence sensing properties. The Cd-MOF film material exhibits sensitive fluorescence responses to nitroaromatic compounds (nitro aromatic compounds) as well as heavy metal cations and anions (Cu2+, Fe3+, and Cr2O72–) and can achieve visual sensing of the three heavy metal ions through distinct color changes from pale yellow to dark yellow or black.