Water oxidation reaction promoted by MIL-101(Fe) photoanode under visible light irradiation

This work spotlights the recently discovered photoelectrocatalytic properties of iron-based metal–organic frameworks (MOFs) for water oxidation reaction (WOR) under visible light irradiation. The low efficiency of WOR is one of the biggest difficulties faced by photoelectrochemical solar energy conversion; the development of new photoanodes for WOR is greatly desired. In view of the fact that a higher efficiency for WOR was forecast thanks to the peculiar properties of MOFs, such as a highly ordered framework and homogenous porous structure, the photoelectrodes based on MIL-101(Fe) containing photo-active iron(III) clusters have been fabricated by using a drop-casting method and applied to photoelectrochemical water oxidation as photoanodes. XRD measurements revealed the successful formation of MIL-101(Fe) electrodes while retaining their framework structures. From the results of photoelectrochemical measurements, the optimal thickness of the MIL-101(Fe) electrodes was determined to be ca. 60 μm, and the optimized MIL-101(Fe) electrode was found to promote photoelectrochemical WOR under visible light irradiation more efficiently than conventional α-Fe₂O₃ electrodes. Moreover, electrochemical impedance spectroscopy measurements demonstrated a lower resistance of charge transfer at the interface between the MOF surface and the electrolyte, resulting in better photoelectrochemical performance of the MIL-101(Fe) electrode.     

Weighted Triangle-free 2-matching Problem with Edge-disjoint Forbidden Triangles

Mathematical Programming - The weighted $${\mathcal {T}}$$ -free 2-matching problem is the following problem: given an undirected graph G, a weight function on its edge set, and a set $${\mathcal...     

Adjacency and transition matrices related to random walks on graphs

Journal of Algebraic Combinatorics - A pointed graph $$(\Gamma ,v_0)$$ induces a family of transition matrices in Wildberger’s construction of a hermitian hypergroup using a random walk on...     

Laser photolysis studies of the reaction of chromium(III) octaethylporphyrin complex with triphenylphosphine and triphenylphosphine oxide

The photoreaction of the chromium(III) octaethylpoprhyrin complex, [Cr(OEP)(Cl)(L)] (L = H2O, Py, OPPh3), in dichloromethane was studied using laser flash photolysis technique. Laser irradiation causes the generation of a coordinately unsaturated intermediate [Cr(OEP)(Cl)], which reacts with ligands in solution to give the parent complex, [Cr(OEP)(Cl)(L)], or a transient species, [Cr(OEP)(Cl)(H2O)], when L = Py or OPPh3. Once produced [Cr(OEP)(Cl)(H2O)] eventually exchanges the axial H2O ligand with L to regenerate [Cr(OEP)(Cl)(L)]. The kinetics of the axial ligand substitution reaction was followed spectrophotometrically, and the ligand-concentration dependence of the ligand exchange rate revealed that the reaction occurs via a limited dissociative mechanism. The photoreaction of [Cr(OEP)(Cl)(OPPh3)] containing excess PPh3 in the bulk solution leads to the unfavorable coordination of the PPh3 molecule to the chromium ion to give a transient complex, [Cr(OEP)(Cl)(PPh3)]. The dynamic and thermodynamic properties of [Cr(OEP)(Cl)(PPh3)] in solution are discussed on the basis of the kinetic parameters of the dissociation and association reactions of the PPh3 ligand together with the steric aspect of the molecular structure of the related complexes.     

Synthesis of vinyloxazolidinones by palladium-catalyzed CO2-recycling reaction of 4-(benzylamino)-2-butenyl carbonates

A CO₂-recycling reaction using (E)-4-(benzylamino)-2-butenyl methyl carbonates has been examined and substituted vinyloxazolidinones were obtained via a CO₂ fixation-elimination process, carried out in the presence of palladium catalyst with DBU.