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Hydrothermal reaction of Co(NO3)2 and terphenyl-3,2",5",3'-tetracarboxyate (H4tpta) generated Co3(OH)2 chains based 3D coordination framework Co3(OH)2(tpta)(H2O)4 (1) that suffered from single-crystal-to-single-crystal dehydration by heating at 160 °C and was transformed into dehydrated Co3(OH)2(tpta) (1a). During the dehydration course, the local coordination environment of part of the Co atoms was transformed from saturated octahedron to coordinatively unsaturated tetrahedron. Heterogenous catalytic experiments on allylic oxidation of cyclohexene show that dehydrated 1a has 6 times enhanced catalytic activity than as-synthesized 1 by using tert-butyl hydroperoxide (t-BuOOH) as oxidant. The activation energy for the oxidation of cylcohexene with 1a catalyst was 67.3 kJ/mol, far below the value with 1 catalysts, which clearly suggested that coordinatively unsaturated CoII sites in 1a have played a significant role in decreasing the activation energy. It is interestingly found that heterogeneous catalytic oxidation of cyclohexene in 1a not only gives the higher conversion of 73.6% but also shows very high selectivity toward 2-cyclohexene-1-one (ca. 64.9%), as evidenced in high turnover numbers (ca. 161) based on the open Co(II) sites of 1a catalyst. Further experiments with a radical trap indicate a radical chain mechanism. This work demonstrates that creativity of coordinatively unsaturated metal sites in MOFs could significantly enhance heterogeneous catalytic activity and selectivity. [ABSTRACT FROM AUTHOR]

Four novel coordination polymers, [Mn2(cptc)(2,2′-bpy)(H2O)]·H2O (1), [Mn2(cptc)(phen)(H2O)]·H2O (2), Mn4(cptc)2(phen)4(H2O)2]·3H2O (3) and [Cd2(cptc)(H2O)3] (4) (H4cptc = cyclopentane-1,2,3,4-tetracarboxylic acid, 2,2′-bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline), have been synthesized by hydrothermal reactions of flexible (1S,2S,3R,4R)-H4cptc with MnCl2/CdCl2. By breaking the mirror plane of symmetry, the meso-cptc ligand is successfully converted into two pairs of enantiomers, the (1R,2S,3S,4R)- and (1S,2R,3R,4S)-cptc groups in 1–3are unprecedented while the documented (1R,2R,3R,4S)- and (1S,2S,3S,4R)-cptc enantiomers exhibit an unprecedented μ6-mode in 4. Layered 1and 2show similar structures and are constructed by centrosymmetric tetranuclear units. 3is a binodal (3,4)-connected layer with Schläfli symbols of (53)2(54·82), in which cptc exhibits two types of μ5-mode bonding. 4has a 3-D pillar layered structure composed of neutral [Cd(cptc)]nlayers and octahedral CdO6pillars. The presence probability of different enantiomers is in agreement with the relative stability of different conformations of cptc calculated by time-dependent density functional theory (TD-DFT). [ABSTRACT FROM AUTHOR]