Luminescent Coordination Polymer with Its Multistimuli-Responsive Sensitivity Enabled and Boosted by Its Dual Emission

Abstract

Multistimuli-responsive luminescent materials have wide and promising applications but their designs and syntheses are very challenging. Here, we report a new dual-emitting Eu-based multiemissive coordination polymer (CP, 1) that can respond to different stimuli, i.e., grinding, pH, and aspartic acid (Asp). 1 exhibits a mechanoluminescence (MCL) property with a visible color change (pink ⇌ blue) upon grinding and can be restored upon exposure to dimethylformamide (DMF) vapor. Moreover, it undergoes a reversible color switching (pink ⇌ blue) with the pH interval in the range of 3–4 and can serve as a selective, reusable, and fast ratiometric probe for Asp in aqueous media, with a limit of detection (LOD) down to 2.48 μM. Moreover, a rapid, highly sensitive, and visualizable response to Asp is demonstrated using a CP-based luminescent film and logic device. Detailed mechanism studies including characterization of single-crystal-to-single-crystal transformation reveal that the multistimuli-responsive property is due to the different responses of the two emissions to the mechanical and pH stimuli and the accompanying changes in the energy transfer efficiency from the ligand to the Eu3+ ion (antenna effect). Multiemissive coordination polymers can be a very promising candidate for multistimuli-responsive luminescent materials with significantly improved functionalities to meet diverse applications.