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)(H2 O)2 ]⋅3 H2 O (1), [Tb(HL)(DMF)(H2 O)2 ] 3 H2 O (2), [Cd4 (L)2 (DMF)4 (H2 O)2 ] 3 H2 O (3) and [Zn3 (HL)2 (H2 O)2 ] 2 DMF⋅7 H2 O (4), have been constructed from a new resorcin[4]arene-functionalized tetracarboxylic acid (H4 L=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 HL(3-) 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 Fe(3+) , 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 Fe(3+) and POMs detection in aqueous solutions employing resorcin[4]arene-based luminescent Ln-MOFs. Furthermore, the possible mechanism of the sensing properties is deduced.