Tandem Visual Recognition of Cu2+ and Chiral Tartaric Acid by Sequence Gel Formation and Collapse

A chiral gelator (<i>R</i>)-H₆L with multiple carboxyl groups based on a 1,1'-bi-2,2'-naphthol (BINOL) skeleton was prepared, and it could form a supramolecular gel under the induction of water in DMSO/H₂O and DMF/H₂O (1/1, <i>v</i>/<i>v</i>). In the EtOH/H₂O system, the original partial gel transformed into a stable metal-organic gel (MOG), specifically with Cu²⁺ among 20 metal ions. It is proposed that Cu²⁺ coordinates with the carboxyl groups of (<i>R</i>)-H₆L to form a three-dimensional network structure. With the addition of a variety of α-hydroxy acids and amino acids, the Cu²⁺-MOG collapsed with merely 0.06 equivalents of L-tartaric acid (L-TA), while other acids required much larger amounts to achieve the same effect, realizing the visual chemoselective and enantioselective recognition of tartaric acid. Therefore, the chiral gelator (<i>R</i>)-H₆L achieved the tandem visual recognition of Cu²⁺ and chiral tartaric acid by sequence gel formation and collapse, offering valuable insights for visual sensing applications and serving as a promising model for future chiral sensor design.