Transition-metal-based (Zn2+ and Cd2+) metal-organic frameworks as fluorescence “turn-off” sensors for highly sensitive and selective detection of hydrogen sulfide

Abstract

Two new coordination polymers of [Zn(L)(4,4′-bpy)0.5].(H2O)0.25(1) and [Cd4(L)4(4,4′-bpy)2].(H2O)(2) have been solvothermally synthesized from semi-rigid ligand H2L (H2L=4,4′-dicarboxy-4″-nitrotriphenylamine) and auxiliary ligand 4,4′-bpy (4,4′-bpy=4,4′-bipyridine), which have been fully characterized by single-crystal X-ray diffraction, PXRD, IR and elemental analysis. Compound 1 is composed of interdigitated 2-D square-grid layers which are assembled from 1-D beaded chain pillared by 4,4′-bpy, whereas compound 2 comprises two interpenetrated 3-Dpcu nets which are constructed by 4,4′-bpy pillared 2-D square-grid layers. Compound 1–2 display both thermal stability and hydrolytic robustness. What is the most interesting finding is that both compounds exhibit strong luminescence in aqueous solution, and each of them can serve as a highly sensitive and selective fluorescence “turn-off” sensor for aqueous detection of hydrogen sulfide.