A photochromic Cd()-organic framework showing highly efficient dual-response sensing properties

Photochromic materials have been found to be promising for a broad range of applications. However, it remains a great challenge to develop new photochromic materials. In this work, a dihydroanthracene-based photochromic organic molecule 9,10-bis(di(pyridine-4-yl)methylene)-9,10-dihydroanthracene ( L ) was developed as a functional ligand to construct a LMOF-based sensor material [Cd 2 L (HBTC) 2 ·2H 2 O·2i-PrOH] n ( 1 ) (LMOF = luminescent metal-organic framework; H 3 BTC = benzene-1,3,5-tricarboxylic acid; i-PrOH = isopropanol). 1 is constructed using a 6-connected [Cd 2 (COO) 2 ] 2+ cluster, a 4-connected L unit and a HBTC double-bridge and exhibits a two-dimensional (2-D) (4,6)-connected architecture. 1 has good water and thermal stability. Before and after photochromism, this LMOF exhibits different luminescence properties, which results in dual-response and highly selective sensing properties. 1 can detect TNP with high sensitivity and selectivity in aqueous media by luminescence quenching effects. More importantly, 1′ ( 1 after photochromism) shows ultrahigh sensing sensitivity and selectivity towards MnO 4 − (the second highest K sv of 4.08 × 10 5 M −1 ). Furthermore, 1′ can identify MnO 4 − in the presence of a similar strong oxidizing anion Cr 2 O 7 2− . In addition, quenching sensing mechanisms are discussed in detail. This work will contribute to the development of highly efficient dual-response sensors. A photochromic Cd( ii )-organic framework shows highly efficient dual-response sensing behavior towards TNP and MnO 4 − .