Experimental Studies and Mechanism Analysis of High-Sensitivity Luminescent Sensing of Pollutional Small Molecules and Ions in Ln4O4 Cluster Based Microporous Metal-Organic Frameworks

Two new isostructural 3D lanthanide metal-organic frameworks (Ln-MOFs) {[Ln(4)(mu(3)-OH)(4)(BPDC)(3)(BPDCA)(0.5)(H2O)(6)]ClO4 center dot 5H(2)O}(n) (Ln = Tb (1) and Gd (2), BPDC2- = 3,3'-dicarboxylate-2,2'-dipyridine anion and BPDCA(2-) = biphenyl-4,4'-dicarboxylate anion) based on cubane-shaped [Ln(4)(mu(3)-OH)(4)](8+) clusters were successfully synthesized and fully characterized. There are two kinds of micropores with dimensions of 3.0 x 7.0 angstrom(2) along the b-axis and 4.5 X 5.5 angstrom(2) along the c-axis in the cationic framework. Ln-MOF 1 exhibits an intensive green luminescence triggered by the efficient antenna effect of ligands under UV light. Luminescent studies illustrate that Ln-MOF 1 could be an efficient multifunctional luminescent material for high-sensitivity sensing of small organic molecules, metal cations, and anions, especially for benzene and acetone, Cu2+, and CrO42-. The mechanism of the sensing properties was studied in detail as well. Additionally, this cationic framework also displays fast capture of pollutant CrO42- by anion exchange.