Pentanuclear Yb(III) cluster-based metal-organic frameworks as heterogeneous catalysts for CO2 conversion.

Two porous metal-organic frameworks (MOFs) incorporating pentanuclear Yb(III) clusters and pyridyl-supported tetracarboxylates or pyridyl carboxylic acid-supported tetracarboxylates, Yb-DDPY and Yb-DDIA , are presented, in which the pentanuclear Yb(III) cluster shows uncommon trigonal bipyramidal geometry. Furthermore, the pentanuclear Yb(III) clusters are extended by tetracarboxylates to form a 3D porous framework with uniform M 12 L 8 -cages constructed by 12 pentanuclear Yb(III) clusters and 8 tetracarboxylates with the size of ca. 20 Å × 17 Å. Their highly CO 2 uptake capacity and the existence of Lewis acidic sites make these MOFs promising catalysts for the chemical conversion of CO 2 . These MOFs demonstrate good catalytic activities and recyclability in the cycloaddition of CO 2 and epoxides at 60 °C under 1.0 MPa pressure or at room temperature and atmospheric pressure. In addition, the synergistic effect of the Brønsted acidic –COOH groups and the Lewis acidic Yb(III) sites makes Yb-DDIA exhibit higher catalytic activity towards the cycloaddition of CO 2 and epoxides. [ABSTRACT FROM AUTHOR]