Systematic Investigation of High-Sensitivity Luminescent Sensing for Polyoxometalates and Iron(III) by MOFs Assembled with a New Resorcin[4]arene-Functionalized Tetracarboxylate

A new family of resorcin[4]arene-based metal-organic frameworks (MOFs), namely, [Eu(HL)(DMF)(H2O)(2)]3H(2)O (1), [Tb(HL)(DMF)(H2O)(2)] 3H(2)O (2), [Cd-4(L)(2)(DMF)(4)(H2O)(2)] 3H(2)O (3) and [Zn-3(HL)(2)(H2O)(2)] 2DMF7H(2)O (4), have been constructed from a new resorcin[4]arene-functionalized tetracarboxylic acid (H4L=2,8,14,20-tetra-ethyl-6,12,18,24-tetra-methoxy-4,10,16,22-tetra-carboxy-methoxy-calix[4]arene). Isostructural 1 and 2 exhibit charming 1D motifs built with the cup-like HL3- anions and rare earth cations. Compounds 3 and 4 show a unique sandwich-based 2D layer and a fascinating 3D framework, respectively. Remarkably, compounds 1 and 2 display intensive red and green emissions triggered by the efficient antenna effect of organic ligands under UV light. More importantly, systematic luminescence studies demonstrate that Ln-MOFs 1 and 2, as efficient multifunctional fluorescent materials, show highly selective and sensitive sensing of Fe3+, polyoxometalates (POMs), and acetone, which represents a rare example of a sensor for quantitatively detecting three different types of analytes. This is also an exceedingly rare example of Fe3+ and POMs detection in aqueous solutions employing resorcin[4]arene-based luminescent Ln-MOFs. Furthermore, the possible mechanism of the sensing properties is deduced.