Yuhei Miyazaki

Photocatalytic hydrogen production from water using porous material [Ru2(p-BDC)2]n

We have detected the first example of open porous metal–organic frameworks (MOFs) that functions as an activity site for the reduction of water into hydrogen molecules in the presence of Ru(bpy)32+, MV2+, and EDTA–2Na under visible light irradiation. This activity is highly efficient: the turnover number based on MOFs and the apparent quantum yield are 8.16 and 4.82%, respectively. Furthermore, this material enables the adsorption of various gases into its pores; its hydrogen uptake capacity is 1.2 wt% at 77.4 K.

Modification of MOF catalysts by manipulation of counter-ions: experimental and theoretical studies of photochemical hydrogen production from water over microporous diruthenium (II, III) coordination polymers

In this study we investigated the photochemical production of hydrogen from water using three heterogeneous microporous ruthenium coordination polymers [Ru2(p-BDC)2X] n (p-BDC = 1,4-benzenedicarboxylate, X = Cl, Br and BF4) in the presence of multi-component systems. The order of catalytic performances is [Ru2(p-BDC)2Br] n >[Ru2(p-BDC)2BF4] n >[Ru2(p-BDC)2Cl] n . The most active catalyst, [Ru2(p-BDC)2Br] n , caused the evolution of 46.7 μmol hydrogen molecules with a turn-over number of 18.7 based on [Ru2(p-BDC)2Br] n under visible light irradiation for 4 h. We ascertained that the differences in catalytic activities originated from (1) the efficiency of the quenching of methyl-viologen radicals by [Ru2(p-BDC)2X] n and (2) the durability of the structure in the reaction. In order to examine the catalytic reaction mechanism, we performed theoretical calculations for neutral model structures [Ru2(HCOO)4X(H2O)] (X = Cl, Br), one-electron reduction model complexes [Ru2(HCOO)4X(H2O)]− and deduced intermediate model structures [H–Ru2(HCOO)4X] using broken-symmetry hybrid density functional theory methods.

Theoretical study of absorption spectrum of dirhodium tetracarboxylate complex [Rh2(CH3COO)4(H2O)2] in aqueous solution revisited

The electronic structures of ground and excited states of [Rh2(CH3COO)4(H2O)2] in aqueous solution are studied using a density functional theory (DFT) with a time-dependent (TD) method. Up to now, several theoretical assignments and explanations of its excitation characters have been reported based on the absorption spectra. In this study, we reinvestigate its absorption spectrum by the TD-DFT approach with the polarisable continuum model in order to clarify the excitation characters of the complex, especially in the aqueous solution well.