Manganese Cyclotriphosphazene Multicarboxylate Frameworks and Composite Encapsulated 1,3,6,8-Tetrakis(p‑benzoic acid) Pyrene as Visualization of Highly Selective Fluorescence Sensors for Aromatic Compounds with NH2/NO2 Group

A novel multilevel channel 3D network organic framework, [H3O] [Mn3(CPCP)­(CH3COO)­(DMF)]·11H2O (Mn-MOF, CPCP = hexa-(4-carboxyl-phenoxy)-cyclotriphosphazene, and DMF = dimethylformamide), was successfully synthesized. Interestingly, Mn-MOF exhibited stimuli-responsive luminescence enhancement after the encapsulation of 1,3,6,8-tetrakis­(p-benzoic acid) pyrene (H4TBAPy) stimulated luminescent intensity enhancement through host–guest processes of the pores in MOFs, especially for o-phenylenediamine and p-nitrobenzoic acid. As a ratiometric luminescence “turn-on” sensor for o-phenylenediamine detection, the transition from blue emission to green emission is of great significance in visual fluorescence detection. After adding p-nitroaniline and o-nitrophenol to the Mn-MOF@H4TBAPy solution, the quenching efficiency was optimized. When the concentration of p-nitroaniline was 0.001 mol/L, the K sv was 5.19 × 104 M–1, and the detection limit was 2.04 μM. When the concentration of o-nitrophenol was 0.001 mol/L, the K sv is 2.4 × 104 M–1, and the detection limit is 4.28 μM. Therefore, Mn-MOF@H4TBAPy could detect p-nitroaniline and o-nitrophenol as a fluorescence sensor with “turn off”.