Highly Luminescent Metal–Organic Frameworks Based on an Aggregation-Induced Emission Ligand as Chemical Sensors for Nitroaromatic Compounds

Three new luminescent metal–organic frameworks (LMOFs) based on d10 metals (Zn2+, Cd2+) and the highly emissive aggregation-induced emission ligand 1,1,2,2-tetrakis(4-(4-carboxyphenyl)phenyl)ethene(H4tcbpe) are reported, with the formulas [Cd3(tcbpe)1.5(DMF)(H2O)2]·(DMF)6·(C2H5OH)3 (1), [Zn(tcbpe)(DMF)]·(MeCN) (2), and [Cd(tcbpe)]·(MeCN) (3). Compounds 1 and 2 both emit strong green light with internal quantum yields (IQYs) as high as 66.8% and 65.7%, respectively, while compound 3 emits bluish green light with 37.2% IQY. A solution-phase sensing study shows that 1 has the highest sensitivity to nitroaromatic compounds and demonstrates that it is potentially useful as a luminescence-based chemical sensor. Density functional theory calculations are used to explain the sensing mechanism and relative sensitivity of compound 1 to various nitroaromatic compounds.