Bifunctional Lanthanide-Based Coordination Polymers: Conversion of CO₂ and Highly Selective Luminescence Sensing for...

A series of bifunctional Ln(III)-based coordination polymers (CPs) {Ln(L)(DMA)₂(NO₃)} [Ln(III) = Eu (1), Gd (2), and Dy (3); organic ligand H₂L = 2,2'-(1,3,5,7-tetrahydroxyoctahydro-4,8-ethanopyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)diacetic acid)] have been successfully synthesized. CPs 1-3 are isostructural and constructed from the dimeric Ln₂ unit in which two adjacent Ln^III ions are bridged by two μ₃-carboxyl oxygens, and the Ln₂ dimeric unit is connected by two NO₃^- ions, four DMA molecules, and four completely protonated L^2- ligands forming a 2D layer structure. The magnetic research reveals that CP 2 shows a significant cryogenic magnetocaloric effect (-ΔS_m = 22.9 J kg^-1 K^-1; T = 2.0 K and ΔH = 7.0 T), whereas CP 3 exhibits slow magnetic relaxation property under H_dc = 0 Oe field. Additionally, the luminescence explorations revealed that CP 1 can act as a recyclable luminescent probe for pollutant acetylacetone among various small organic solvent molecules, and the corresponding detection limit is 10^-7 mol/L. More importantly, CP 1 also exhibits good catalytic performance in the cycloaddition reaction of CO₂ and epoxides or cyanamides under mild conditions. As far as we know, CP 1 represents the first bifunctional lanthanide homogeneous catalyst that can efficiently catalyze the reaction of cyanamides/epoxides with CO₂ simultaneously.