Synthesis and Characterization of New Ce(IV)-MOFs Exhibiting Various Framework Topologies

We report on the applicability of an easy general synthesis procedure for the formation of Ce(IV)-MOFs which contain hexanuclear clusters. Thus, the series of Ce(IV)-based MOFs isoreticular to their Zr analogues has been extended to reo and spn topologies. Four new MOFs denoted as Ce-UiO-66-BPyDC [Ce6(μ3-O)4(μ3-OH)4(BPyDC)6] (BPyDC2– = 2,2′-bipyridine-5,5′-dicarboxylate), Ce-DUT-67-PZDC [Ce6(μ3-O)4(μ3-OH)4(PZDC)4(OH)4(H2O)4] (PZDC2– = 3,5-pyrazoledicarboxylate), Ce-DUT-67-TDC [Ce6(μ3-O)4(μ3-OH)4(TDC)4(OH)4(H2O)4] (TDC2– = 2,5-thiophenedicarboxylate), and Ce-MOF-808 [Ce6(μ3-O)4(μ3-OH)4(BTC)2(OH)6(H2O)6] (BTC3– = benzene-1,3,5-tricarboxylate) were obtained under mild reaction conditions (100 °C) and after short reaction times (15 min) using a modulated synthesis approach. The MOFs differ in their connectivity of the [Ce6O4(OH)4(−CO2)x] (x = 12, 8, 6) cluster, the geometry of the organic linker molecules (linear and bent dicarboxylic acids, tricarboxylic acid), and the resulting topology (fcu, reo, spn). The structures of all Ce-MOFs were confirmed using PXRD data by Rietveld refinement and Le Bail fitting. The heterocyclic aromatic dicarboxylic acids H2PZDC and H2TDC lead to MOFs which are both isostructural to DUT-67 due to the similar linker geometries. Ce-UiO-66-BPyDC and Ce-MOF-808 are thermally stable up to 330 and 150 °C, respectively, as proven by VT-PXRD measurements. N2 sorption experiments reveal large specific surface areas of 2120 m2 g–1 for Ce-UiO-66-BPyDC and 1725 m2 g–1 for Ce-MOF-808.