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

[This corrects the article DOI: 10.3389/fchem.2018.00514.].

An Anthracene-Based Metal-Organic Framework for Selective Photo-Reduction of Carbon Dioxide to Formic Acid Coupled with Water Oxidation.

A Zr-based metal-organic framework has been synthesized and employed as a catalyst for photochemical carbon dioxide reduction coupled with water oxidation. The catalyst shows significant carbon dioxide reduction property with concomitant water oxidation. The catalyst has broad visible light as well as UV light absorption property, which is further confirmed from electronic absorption spectroscopy. Formic acid was the only reduced product from carbon dioxide with a turn-over frequency (TOF) of 0.69 h-1 in addition to oxygen, which was produced with a TOF of 0.54 h-1 . No external photosensitizer is used and the ligand itself acts as the light harvester. The efficient and selective photochemical carbon dioxide reduction to formic acid with concomitant water oxidation using Zr-based MOF as catalyst is thus demonstrated here.

Electrocatalytic Reduction of CO2 to Acetic Acid by a Molecular Manganese Corrole Complex.

The controlled electrochemical reduction of carbon dioxide to value added chemicals is an important strategy in terms of renewable energy technologies. Therefore, the development of efficient and stable catalysts in an aqueous environment is of great importance. In this context, we focused on synthesizing and studying a molecular MnIII -corrole complex, which is modified on the three meso-positions with polyethylene glycol moieties for direct and selective production of acetic acid from CO2 . Electrochemical reduction of MnIII leads to an electroactive MnII species, which binds CO2 and stabilizes the reduced intermediates. This catalyst allows to electrochemically reduce CO2 to acetic acid in a moderate acidic aqueous medium (pH 6) with a selectivity of 63 % and a turn over frequency (TOF) of 8.25 h-1 , when immobilized on a carbon paper (CP) electrode. In terms of high selectivity towards acetate, we propose the formation and reduction of an oxalate type intermediate, stabilized at the MnIII -corrole center.

pH-induced phase transition and crystallization of soft-oxometalates (SOMs) into polyoxometalates (POMs): a study on crystallization from colloids.

In this work, we demonstrate a simple approach for growing 1D (one-dimensional) inorganic chains of K(C6H16N)3Mo8O26·H2O polyoxometalates (POMs) from its colloidal soft-oxometalate (SOM) phase through the variation of pH. The structure is composed mainly of a 1D inorganic chain with a ß-Mo8O264- binding node linked using K+ via Mo-O-K linkages, which results in a cuboctahedral geometry for the K+ ions. Crystal structure and Hirshfeld surface studies reveal the role of triethylammonium cations in restricting the growth of the 1D chain into 2D/3D (two-/three-dimensional) structures. During the nucleation process from the heterogeneous SOM phase, some of the intermolecular interactions in the dispersion phase are retained in the crystal structure, which was evidenced from residual O...O interactions. The crystallization of the species from its colloidal form as a function of pH was studied by the use of Raman spectroscopy and it was found that the increase in volume fraction of the ß-Mo8O264- species in the crystallizing colloidal mixture with the decrease in pH is responsible for the nucleation. This was monitored by time-dependent DLS (dynamic light scattering) measurement and zeta-potential studies, revealing the co-existence of both the crystal and the colloidal forms at pH 3-2. This brings us to the conclusion that in the crystallization of POMs, the colloidal SOM phase precedes the crystalline POM phase which occurs via a phase transition. This work could open up avenues for the study of POM formation from the stand-point of colloidal chemistry and SOMs.

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.

(±)-trans-6,6'-Dieth-oxy-2,2'-[cyclo-hexane-1,2-diylbis(nitrilo-methanylyl-idene)]diphenol monohydrate.

In the title hydrate, C24H30N2O4·H2O, the organic mol-ecule adopts an E conformation with respect to the azomethine double bonds. The cyclo-hexane ring is in a chair conformation. The dihedral angle between benzene rings is 79.6 (2)°. Two intra-molecular O-H⋯N hydrogen bonds are present. In the crystal, the components are linked by O-H⋯O hydrogen bonds and weak C-H⋯π inter-actions, generating a three-dimensional supramolecular architecture.

2-Eth-oxy-6-({2-[(3-eth-oxy-2-hy-droxy-benzyl-idene)amino]-benz-yl}imino-meth-yl)phenol.

The title compound, C(25)H(26)N(2)O(4), exists in an E conformation with respect to each azomethine link. The two phenol-substituted benzene rings are twisted away from the plane of the diimine benzene ring by dihedral angles of 27.25 (5) and 56.67 (5)°. The mol-ecular structure is stabilized by intra-molecular O-H⋯N hydrogen bonds.