Supporting Information

A Novel Photocatalytic System Constructed using Eosin Y, Titanium Dioxide, and Keggin-Type Platinum(II)- and Aluminum(III)-coordinated Polyoxotungstates for Hydrogen Production from Water under Visible Light Irradiation

Shota Hattori • Yuki Ihara • Chika Nozaki Kato

Preparation of [(CH3)4N]6H[a2-P2W17{Al(OH2)}O61]∙11H2O (TMA-Al-4).

A solution of Al(NO3)3∙9H2O (0.375 g; 1.0 mmol) dissolved in 7.5 mL of water was added to a solution of K10[a2-P2W17O61]∙27H2O (5.041 g; 1.0 mmol) dissolved in 50 mL of water at 70 ºC. After stirring for 3 h at 25 ºC, a solid tetramethylammonium chloride (3.288 g; 30 mmol) was added to the solution. A white precipitate was collected by a membrane filter (JG 0.2 mm) and washed with a small amount of ethanol. At this stage, a crude product was obtained in a 4.743 g yield. For purification, the crude product (4.734 g) was dissolved in 285 mL of water at 70 oC; the resulting solution was filtered through a membrane filter (JG 0.2 mm). After standing in a refrigerator overnight, a white precipitate was collected by a membrane filter (JG 0.2 mm) to yield 0.111 g of product. The percent yield was calculated on the basis of [mol of TMA-Al-4]/[mol of K10[a2-P2W17O61]∙27H2O] ´ 100 and was 2.29%. Elemental analysis results showed C, 6.15; H, 1.79; N, 1.91%. Calculations for [(CH3)4N]6H[a2-P2W17{Al(OH2)}O61]∙xH2O (x = 2) = C24H79Al1N6O64P2W17: C, 6.15; H, 1.70; N, 1.79%. A weight loss of 3.51% was observed during overnight drying at room temperature under 10-3–10-4 torr before analysis, which suggests the presence of 9 weakly solvated or adsorbed water molecules (3.34%). TG/DTA under atmospheric conditions showed a weight loss of 4.50% without a clear endothermic point observed below 130 °C (4.46% correspond to 12 water molecules, based on calculations). Additionally, a weight loss of 9.32% with an exothermic peak at 389.5 °C was observed in the temperature range from 312 to 474 oC (9.17% correspond to six [(CH3)4N]+ cations based on calculations). The IR (KBr disk) results in the 1300 – 400 cm-1 region (polyoxometalate region) were as follows: 1092s, 1016w, 950s, 914s, 798s, and 706m cm-1. The NMR results gave 31P NMR: (D2O, 23.0 oC): d -10.14, -13.40. These spectral results were the same as those of K7[a2-P2W17{Al(OH2)}O61]×14H2O.

Figure S1. Time course for hydrogen evolution from aqueous TEOA solution under visible light irradiation (³400 nm). Reaction conditions: Cs-Pt-1 (1.0 mmol of Pt), EY (2.5 mmol), 100 mM aqueous TEOA solution (10 mL, pH 7), at 25 ºC.

Figure S2. Time course for hydrogen evolution from aqueous TEOA solution under visible light irradiation (³440 nm). Reaction conditions: Cs-Pt-1 (1.9 mmol of Pt), EY (5.0 mmol), 100 mM aqueous TEOA solution (10 mL, pH 10), at 25 ºC.

Figure S3. 31P NMR spectra in D2O of Cs-Pt-1 (b) before and after (b) 1-h, (c) 2-h, and (d) 3-h light irradiation. The reaction conditions: Cs-Pt-1 (4.0 mmol) was dissolved in a 100 mM aqueous TEOA solution (5 mL) at 25 °C. EY (6.6 mmol) was added to the solution, and light (³400 nm) was irradiated for 1 - 3 h. The spectra were referenced to an external standard of 85% H3PO4 in a sealed capillary.

Figure S4. Time course for hydrogen evolution from aqueous TEOA solution under visible light irradiation (³440 nm). Reaction conditions: Cs-Pt-1 (0.2 mmol of Pt), EY (2.5 mmol), K-Al-1 (2.5 mmol), 100 mM aqueous TEOA solution (10 mL, pH 7), at 25 ºC.

Figure S5. UV-vis spectra (a) in 100 mM aqueous TEOA solution at pH 7 of a mixture of Cs-Pt-1 (0.2 mmol of Pt), EY (2.5 mmol), and K-Al-1 (2.5 mmol), (b) in 100 mM aqueous TEOA solution at pH 7 (10 mL) of after 6 h of light irradiation (³400 nm) in the presence of K-Al-1, and (c) in 100 mM aqueous TEOA solution at pH 7 after 6 h of light irradiation (³400 nm) in the absence of K-Al-1.

Figure S6. UV-vis spectra in 100 mM aqueous TEOA solution (10 mL) at pH 7 of (a) a mixture of Cs-Pt-1 (10 mmol) and EY (2.8 mmol) and (b) a mixture of cisplatin (1.3 mmol), EY (2.8 mmol), and K-Al-1 (10 mmol).

Figure S7. Time course for hydrogen evolution from an aqueous TEOA solution under visible light irradiation. Pretreatment and reaction conditions: a 100 mM aqueous TEOA solution (pH 7; 10 mL) containing Cs-Pt-1 (0.2 mmol of Pt), EY (2.5 mmol), K-Al-1 (2.5 mmol), TiO2 (anatase: rutile = 80 : 20) (50 mg) was irradiated by visible light (³440 nm) for 6 h. The hydrogen generated during 6-h light irradiation was degassed, and the Cs-Pt-1/EY/K-Al-1/TiO2 system was reused in the second run under ³440 nm light irradiation at 25 ºC.

Figure S8. A probable reaction mechanism for hydrogen evolution from a TEOA aqueous solution catalyzed for Cs-Pt-1/EY/K-Al-1/TiO2 system under visible light irradiation.