Heterometallic In(III)–Pd(II) Porous Metal–Organic Framework with Square-Octahedron Topology Displaying High CO2 Uptake and Selectivity toward CH4 and N2

The targeted synthesis of metal–organic frameworks (MOFs) with open metal sites, following reticular chemistry rules, provides a straightforward methodology toward the development of advanced porous materials especially for gas storage/separation applications. Using a palladated tetracarboxylate metalloligand as a 4-connected node, we succeeded in synthesizing the first heterobimetallic In(III)/Pd(II)-based MOF with square-octahedron ( soc ) topology. The new MOF, formulated as [In 3 O( L ) 1.5 (H 2 O) 2 Cl]·n(solv) ( 1 ), features the oxo-centered trinuclear clusters, [In 3 (μ 3 -O)(−COO) 6 ], acting as trigonal-prismatic 6-connected nodes that linked together with the metalloligand trans -[PdCl 2 (PDC) 2 ] ( L 4– ) (PDC: pyridine-3,5-dicarboxylate) to form a 3D network. After successful activation of 1 using supercritical CO 2, high-resolution microporous analysis revealed the presence of small micropores (5.8 Å) with BET area of 795 m 2 g –1 and total pore volume of 0.35 cm 3 g –1 . The activated solid shows high gravimetric (92.3 cm 3 g –1 ) and volumetric (120.9 cm 3 cm –3 ) CO 2 uptake at 273 K and 1 bar as well as high CO 2 /CH 4 (15.4 for a 50:50 molar mixture) and CO 2 /N 2 (131.7 for a 10:90 molar mixture) selectivity, with moderate Q st 0 for CO 2 (29.8 kJ mol –1 ). Slight modifications of the synthesis conditions led to the formation of a different MOF with an anionic framework, having a chemical formula [Me 2 NH 2 ][In( L )]· n (solv) ( 2 ). This MOF is constructed from pseudotetrahedral, mononuclear [In(−COO) 4 ] nodes bridged by four L 4– linkers, resulting in a 3D network with PtS topology.