A pH-Stable Tb^III-Based Metal–Organic Framework as a Turn-On and Blue-Shift Fluorescence Sensor toward Benzaldehyde and Salicylaldehyde in Aqueous Solution

Abstract

A new polydentate tetracarboxylic acid with a benzothiadiazole unit (4',4'''-(benzo[<i>c</i>][1,2,5]thiadiazole-4,7-diyl)bis([1,1'-biphenyl]-3,5-dicarboxylic acid), H₄BTDBA) has been used to prepare a pH-stable three-dimensional Tb^III-based metal-organic framework (MOF) with the formula {[(CH₃)₂NH₂]_0.7[Tb₂(BTDBA)_1.5(lac)_0.7(H₂O)₂]·solvents}_n (Hlac = lactic acid, <b>JXUST-19</b>). <b>JXUST-19</b> exhibits a new (4,4,12)-connected topology based on tetranuclear [Tb₄] clusters. <b>JXUST-19</b> can remain stable when soaked in water for at least 1 week and in aqueous solutions with various pH values (2-12) for 24 h. Fluorescence study indicates <b>JXUST-19</b> can be employed as a rare turn-on and blue-shift MOF sensor toward benzaldehyde (BZ) and salicylaldehyde (SA). To date, <b>JXUST-19</b> represents the first Tb^III-based turn-on MOF sensor toward salicylaldehyde in aqueous solution, and the fluorescence enhancement and naked-eye detection of BZ have been rarely reported. In addition, <b>JXUST-19</b> based fluorescent test papers, light-emitting diode lamp beads, and portable composite films were developed to realize naked-eye detection of BZ and SA, which has great potential in practical applications.