Kagóme Cobalt(II)‐Organic Layers as Robust Scaffolds for Highly Efficient Photocatalytic Oxygen Evolution

Abstract

Two Kagóme cobalt(II)-organic layers of [Co3 (μ3 -OH)2 (bdc)2 ]n (1) and [Co3 (μ3 -OH)2 (chdc)2 ]n (2) (bdc=o-benzenedicarboxylate and chdc=1,2-cyclohexanedicarboxylate) that bear bridging OH(-) ligands were explored as water oxidation catalysts (WOCs) for photocatalytic O2 production. The activities of 1 and 2 towards H2 O oxidation were assessed by monitoring the in situ O2 concentration versus time in the reaction medium by utilizing a Clark-type oxygen electrode under photochemical conditions. The oxygen evolution rate (RO2 ) was 24.3 μmol s(-1) g(-1) for 1 and 48.8 μmol s(-1) g(-1) for 2 at pH 8.0. Photocatalytic reaction studies show that 1 and 2 exhibit enhanced activities toward the oxidation of water compared to commercial nanosized Co3 O4 . In scaled-up photoreactions, the pH value of the reaction medium decreased from 8.0 to around 7.0 after 20 min and the O2 production ceased. Based on the amounts of the sacrificial oxidant (K2 S2 O8 ) used, the yield of O2 produced is 49.6 % for 2 and 29.8 % for 1. However, the catalyst can be recycled without a significant loss of catalytic activity. Spectroscopic studies suggest that the structure and composition of recycled 1 and 2 are maintained. In isotope-labeling H2 (18) O (97 % enriched) experiments, the distribution of (16) O(16) O/(16) O(18) O/(18) O(18) O detected was 0:7.55:92.45, which is comparable to the theoretical values of 0.09:5.82:94.09. This work not only provides new catalysts that resemble ligand-protected cobalt oxide materials but also establishes the significance of the existence of OH(-) (or H2 O) binding sites at the metal center in WOCs.

Light-Assisted Catalytic Water Oxidation from Porphyrin J-Aggregate

“…By far, most reported photocatalysts for water oxidation are active at high pH, but may be deactivated in acid solution . Some are even lost the photocatalytic capacity in neutral pH range . Nakamura et.…”

Unusual Formation of CoO@C “Dandelions” Derived from 2D Kagóme MOLs for Efficient Lithium Storage

“…In the as-synthesized structure, ultrathin CoO nanowires are confined in continuous ultrathin graphitic carbon and assemble preferentially into 3D arrays. [22] Briefly, Co(NO 3 ) 2 ·6H 2 O with equimolar o-benzenedicarboxylate acid was fed into CH 3 OH-H 2 O to form a transparent solution at room temperature under magnetic stirring ( Figure 1A). Additionally, the open space between neighboring nanowires not only allows for easy permeation of the electrolyte but also alleviates the volume change upon Li + insertion/extraction.…”

“…Specifically, the 2D Kagóme MOL precursor was first synthesized by a typical solvothermal method. According to our previously reported procedure, its structure was found via X‐ray single‐crystal diffraction to be formulated by [Co 3 ( µ ‐OH) 2 ( o ‐benzenedicarboxylate) 2 ] n (Figure A–C) . Briefly, Co(NO 3 ) 2 ·6H 2 O with equimolar o ‐benzenedicarboxylate acid was fed into CH 3 OH‐H 2 O to form a transparent solution at room temperature under magnetic stirring (Figure A).…”

Antiferromagnetically coupled double perovskite as an efficient and robust catalyst for visible light driven water splitting at neutral pH

“…A comparative study using reported materials with similar instrumental set ups is tabulated in Table 3. 25,60–65 The present CLSR material is superior compared with many reported mixed metal oxides as well as polyoxometalates. Though the amount of the catalysts is varied in materials, the trend of our results for oxygen evaluation is really encouraging in the similar class of materials.…”