The mechanism of CO2 hydration: a porous metal oxide nanocapsule catalyst can mimic the biological carbonic anhydrase role

Sequential Isomerization of a Macrocyclic Polyoxometalate Archetype

Controlled isomerization of individual {α-P₂W₁₂O₄₈} polyoxotungstate building blocks under the constricted conditions of the macrocyclic [P₈W₄₈O₁₈₄]^40- archetype ({P₈W₄₈}) is linked to site-specific Cu^II coordination. The derivatives [αγαγ-P₈W₄₈O₁₈₄{Cu(H₂O)}₂]^36- (1), [γγγγ-P₈W₄₈O₁₈₄{Cu(H₂O)_0.5}₄]^32- (2), and [αγγγ-P₈W₄₈O₁₈₄{Cu(H₂O)}₃]^34- (3) feature the {αγαγ-P₈W₄₈} and the hitherto unknown {γγγγ-P₈W₄₈} and {αγγγ-P₈W₄₈} isomers based on {α-P₂W₁₂} and/or Cu^II-stabilized {γ-P₂W₁₂} units and form from the reactions of the classical {P₈W₄₈} (={αααα-P₈W₄₈}) and CuCl₂ in sodium acetate medium (pH 5.2). All products were thoroughly characterized in both the solid state and aqueous solutions, including electrocatalysis assessments.

Evaluation of the chemo- and shape-selective association of a bowl-type dodecavanadate cage with an electron-rich group

The host-guest interaction between a half spherical-type dodecavanadate (V12) and a neutral molecule guest was evaluated by monitoring the flip of a VO₅ unit caused by the presence or absence of a guest in the cavity of V12. In N,N-dimethylformamide (DMF), V12 adopted the guest-free form (V12-free). By the addition of several guest molecules, such as acetonitrile, nitromethane, and dichloromethane, the structural conversion to the guest-inserted form (V12(guest)) was observed with the affinity constants of 137 ± 10 M^-1, 0.14 ± 0.1 M^-1, and 0.15 ± 0.1 M^-1, respectively. In the case of 1,2-dichloroethane, 1,2-dibromoethane, and 1,2-diiodoethane, the constants were 35 ± 5 M^-1, 114 ± 5 M^-1, and 2.1 ± 0.5 M^-1, respectively, suggesting that the bromo group is the best fit to the cavity of the bowl. A cyclic carbonate, 5- and 6-membered lactones, cyclobutanone, and hexanal were inserted into the V12 host, while a non-cyclic carbonate, non-cyclic and 7-membered cyclic ester, a ketone with a 5-membered ring, and benzaldehyde showed no effect on the guest insertion. The V12 host preferred to hold a guest with an electron-rich group, and the bowl-type structure showed the unique shape-selective interaction with the guest.

A Molecular CO2 Reduction Catalyst Based on Giant Polyoxometalate {Mo368}

Photocatalytic CO2 reduction in water is one of the most attractive research pursuits of our time. In this article we report a giant polyoxometalate {Mo368} based homogeneous catalytic system, which efficiently reduces CO2 to formic acid with a maximum turnover number (TON) of 27,666, turnover frequency (TOF) of 4,611 h-1 and external quantum efficiency of the reaction is 0.6%. The catalytic system oxidizes water and releases electrons, and these electrons are further utilized for the reduction of CO2 to formic acid. A maximum of 8.3 mmol of formic acid was observed with the loading of 0.3 μmol of the catalyst. Our catalyst material is also stable throughout the reaction. The starting materials for this experiment are CO2 and H2O and the end products are HCOOH and O2. The formic acid formed in this reaction is an important H2 gas carrier and thus significant in renewable energy research.

Electronic Structure Studies on the Whole Keplerate Family: Predicting New Members

A comprehensive study of the electronic structure of nanoscale molecular oxide capsules of the type [{M^VI (M^VI )₅ O₂₁ }₁₂ {M'^V₂ O₂ (μ-X)(μ-Y)(L^n- )}₃₀ ]^(12+n)- is presented, where M,M'=Mo,W, and the bridging ligands X,Y=O,S, carried out by means of density functional theory. Discussion of the electronic structure of these derivatives is focused on the thermodynamic stability of each of the structures, the one having the highest HOMO-LUMO gap being M=W, M'=Mo, X=Y=S. For the most well-known structure M=M'=Mo, X=Y=O, [Mo₁₃₂ O₃₇₂ ]^12- , the chemical bonding of several ligands to the {Mo^V₂ O₂ (μ-O)₂ } linker moiety produces negligible effects on its stability, which is evidence of a strong ionic component in these bonds. The existence of a hitherto unknown species, namely W₁₃₂ with both bridging alternatives, is discussed and put into context.

Anions coordinating anions: analysis of the interaction between anionic Keplerate nanocapsules and their anionic ligands

Keplerates are a family of anionic metal oxide spherical capsules containing up to 132 metal atoms and some hundreds of oxygen atoms. These capsules holding a high negative charge of -12 coordinate both mono-anionic and di-anionic ligands thus increasing their charge up to -42, even up to -72, which is compensated by the corresponding counter-cations in the X-ray structures. We present an analysis of the relative importance of several energy terms of the coordinate bond between the capsule and ligands like carbonate, sulphate, sulphite, phosphinate, selenate, and a variety of carboxylates, of which the overriding component is contributed by solvation/de-solvation effects.