Luminescent Metal–Organic Framework with Outstanding “Turn-On” Hg<sup>2+</sup> Sensing Ability First Constructed by an AIE Ligand
Jinfang Zhang, Xingyu Tao, Yinlong Yue, Dejing Yin, Chi Zhang
Abstract
Hg 2+ is highly toxic and can cause serious harm to the environment and humans. Thus, it is vital to develop efficient Hg 2+ sensors. In this work, a LMOF-based (LMOF = luminescent metal–organic framework) “turn-on” Hg 2+ sensor ( 1 ) is first developed by an aggregation-induced emission (AIE) functional ligand. 1 with a formula of [Cd 3 ( L ) 2 (NDA) 3 (H 2 O) 2 · ( L )(MeOH)] n ( L = 4,4′-((2,7-di- tert -butyl-9 H -fluoren-9-ylidene)-methylene)dipyridine; H 2 NDA = 1,4-naphthalenedicarboxylic acid) exhibits a unique (3,4)-connected 2-D framework with 3-connected Cd1, 4-connected [Cd 2 (COO) 3 ] + cluster, and L and NDA 2– bridges. The fluorene rings of L in 1 stack in a back-to-back manner. 1 has excellent water, pH, and thermal stabilities and can “turn-on” detect Hg 2+ with ultrahigh sensitivity, good selectivity, and recyclability in a water medium. Furthermore, 1 shows obvious naked-eye-visible emission change and an extremely fast sensing response toward Hg 2+ (<1 S) and can maintain its enhanced intensity over 5 min. The test paper is developed for practical “turn-on” Hg 2+ sensing application. The “turn-on” Hg 2+ sensing mechanism of 1 is discussed in detail.