Supporting Information

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1 Supporting Information Unveiling Charge Separation Dynamics in CdS/Metal-Organic Framework Composites for Enhanced Photocatalysis Hai-Qun Xu,, Sizhuo Yang,, Xing Ma,, Jier Huang,*, and Hai-Long Jiang*, Hefei National Laboratory for Physical Sciences at the Microscale, CAS Key Laboratory of Soft Matter Chemistry, Collaborative Innovation Center of Suzhou Nano Science and Technology, Department of Chemistry, University of Science and Technology of China, Hefei, Anhui , P.R. China Department of Chemistry, Marquette University, Milwaukee, Wisconsin 53201, United States These authors contributed equally to this work. *To whom correspondence should be addressed. (H.-L.J.); (J.H.) S1

2 100 nm Figure S1. TEM image of CdS. a b c 200 nm 100 nm d 200 nm 200 nm Figure S2. a) SEM and b) TEM images of CdS/UiO-66(20). c) SEM and d) TEM images of CdS/UiO-66(40). S2

3 0.336 nm CdS(111) 2 nm Figure S3. HRTEM image of CdS/UiO-66(10). CdS/UiO-66(40) Intensity (a. u.) CdS/UiO-66(20) CdS/UiO-66(10) UiO-66 CdS CdS-PDF Theta (degree) Figure S4. Powder XRD patterns of CdS, UiO-66 and CdS/UiO-66 composites with different CdS loadings. S3

4 (a) CdS/UiO-66(10) Intensity (a. u.) O KL1 Cd 3p1 Cd 3p3 O 1s Cd 3d3 Zr 3s Zr 3p1 Cd 3d5 Zr 3p3 C 1s S 2s Zr 3d S 2p (b) Intensity (a. u.) UiO-66 Zr 3d 3/ ev CdS/UiO-66(10) Zr 3d 3/ ev Zr 3d 5/ ev Zr 3d 5/ ev (c) Binding energy (ev) CdS Cd 3d 3/ ev Cd 3d 5/ ev (d) Binding energy (ev) CdS S 2p 3/ ev S 2p 1/ ev Intensity (a. u.) CdS/UiO-66(10) Cd 3d 3/ ev Cd 3d 5/ ev Intensity (a. u.) CdS/UiO-66(10) S 2p 1/ ev S 2p 3/ ev Binding energy (ev) Binding energy (ev) Figure S5. XPS spectra of the CdS, UiO-66 and CdS/UiO-66(10): a) survey spectrum and high-resolution b) Zr 3d, c) Cd 3d and d) S 2p spectra. Quantity Adsorbed (cm 3 /g) 400 UiO CdS/UiO-66(10) CdS/UiO-66(20) CdS/UiO-66(40) CdS Relative Pressure (P/P 0 ) Figure S6. N2 sorption isotherms (solid: adsorption curve; open: desorption curve) at 77 K for CdS, UiO-66 and CdS/UiO-66(X) with different CdS loadings. S4

5 (a) (b) (c) (d) (e) Figure S7. Photographs of a) UiO-66, b) CdS/UiO-66(10), c) CdS/UiO-66(20), d) CdS/UiO-66(40) and e) CdS dispersed in ethanol. Intensity (a. u.) CdS/UiO-66(10) after 3 runs as-synthesized CdS/UiO-66(10) Theta (degree) Figure S8. Powder XRD patterns for as-synthesized CdS/UiO-66(10) and CdS/UiO- 66(10) after 3 catalytic runs, showing its well retained structure during the catalysis. S5

6 100 nm Figure S9. SEM image of CdS/UiO-66(10) after 3 catalytic runs. 100 nm Figure S10. TEM image of CdS/UiO-66(10) after 3 catalytic runs. S6

7 a 1ps 20ps 200ps 2ns 5ps 50ps 1ns 4ns b 0 A (mod) 0-5 A (a.u.) -1 CdS CdS/MV Wavelength (nm) Time delay (ps) Figure S11. a) Transient absorption spectra of CdS in the presence of MV 2+ following 400 nm excitation. b) The comparison of kinetic traces at 650 nm between CdS and CdS/MV C -2 (F -2 ) LUMO -0.6 V 4.1 ev 3.5 V HOMO -0.8 V 500 Hz 1000 Hz 1500 Hz Potential (V) vs. Ag/AgCl Figure S12. Mott-Schottky plots for UiO-66 in 0.2 M Na2SO4 aqueous solution (ph = 6.8). Inset: Energy diagram of the HOMO and LUMO levels of UiO-66. S7

8 UiO-66 (Ahv) 2 (ev) 2 Eg=4.1 ev Eg (ev) Figure S13. Tauc plot of UiO-66. Mott Schottky plots of UiO-66 were measured at frequencies of 500, 1000, and 1500 Hz. As shown in Figure S12, the positive slope of the obtained C -2 to the potential plot is consistent with that of typical n-type semiconductor. The intersection point is independent on the frequency and the flat band position (Vfb) determined from the intersection is approximately 0.8 V vs. Ag/AgCl (i.e., 0.6 V vs. NHE). Since it is generally accepted that the bottom of the conduction band in many n-type semiconductors is approximately equal to the flat band potential, S1 the lowest unoccupied molecular orbital (LUMO) of UiO-66 is estimated to be 0.6 V vs. NHE. With the band gap energy (Eg) of UiO-66 estimated to be 4.1 ev by a Tauc plot (Figure S13), its highest occupied molecular orbital (HOMO) is then calculated to be 3.5 V vs. NHE (Figure S12). S8

9 12 10 CB 2.4 ev -0.7 V 500 Hz 1000 Hz 1500 Hz 10 8 C -2 (F -2 ) 8 6 VB 1.7 V V Potential (V) vs. Ag/AgCl Figure S14. Mott-Schottky plots for CdS in 0.2 M Na2SO4 aqueous solution (ph = 6.8). Inset: Energy diagram of the CB and VB levels of CdS. CdS (Ahv) 2 (ev) 2 Eg=2.4 ev Figure S15. Tauc plot of CdS Eg (ev) Mott Schottky plots of CdS were measured at frequencies of 500, 1000, and 1500 Hz. As shown in Figure S14, the positive slope of the obtained C -2 to the potential plot is consistent with that of typical n-type semiconductor. The intersection point is S9

10 independent on the frequency and the flat band position (Vfb) determined from the intersection is approximately 0.9 V vs. Ag/AgCl (i.e., 0.7 V vs. NHE). Since it is generally accepted that the bottom of the conduction band in many n-type semiconductors is approximately equal to the flat band potential, S1,S2 the conduction band (CB) of CdS is estimated to be 0.7 V vs. NHE. With the band gap energy (Eg) of CdS estimated to be 2.4 ev by a Tauc plot (Figure S15), its valence band (VB) is then calculated to be 1.7 V vs. NHE (Figure S14). S10

11 Table S1. ICP results for CdS contents in CdS/UiO-66(X) hybrids. Cat. CdS contents (wt%) CdS/UiO-66(10) CdS/UiO-66(20) CdS/UiO-66(40) Table S2. Comparison of CdS/UiO-66(10) composite with other CdS/porous materials photocatalysts. Catalyst Experimental condition Hydrogen evolution rate (μmol h -1 gcds -1 ) Ref. CdS/ETS-4 CdS/ETS g catalyst, 60 ml of water containing Na2S (0.1 M), Na2SO3 (0.5 M) and NaOH (1.0 M), 300 W Xe lamp, λ > 420 nm S3 CdS/SBA-15 ~ 207 CdS/zeolite-Y 0.2 g catalyst, 50 ml of 1:1 ~ 507 ethanol/water, 500 W Hg-Xe arc CdS/zeolite-L large lamp, λ > 400 nm ~ 130 S4 CdS/zeolite-L small ~ 100 CdS@Ti-MCM g catalyst, Na2SO3 (0.38 M, ml) solution, 350 W Xe Pt-CdS@Ti-MCM-41 lamp, λ > 430 nm 875 S5 CdS-Y 0.05 g catalyst, 30 ml of water containing Na2S (0.1 M), Na2SO3 (0.5 M) and NaOH (1.0 M), 200 W Hg (Xe) lamp, S6 S11

12 nm< λ < 570 nm CdS-MCM CdS/Al-MCM-41 CdS-mSiO CdS-Z CdS/UiO-66(10) 0.04 g catalyst, 20 ml of 1:1 ethanol/water, 300 W Xe lamp, λ > 400 nm 0.1 g catalyst, 50 ml aqueous solution of sacrificial reagent (Na2S:Na2SO3 = 5:1, by weight), 350 W Xe lamp, λ >400 nm 0.04 g catalyst, 20 ml of 1:1 ethanol/water, 300 W Xe lamp, λ > 400 nm 0.05 g catalyst, 25 ml aqueous solution containing Na2SO3 (0.8 M) and Na2S (0.6 M) in 1:1 ratio by volume, 288 W ordinary day light fluorescent lamp g catalyst, 31 ml of 27:3:1 CH3CN/lactic acid/h2o, 300 W Xe lamp, λ > 380 nm 1150 S7 802 S8 606 S9 ~ 333 S this work S12

13 Table S3. The apparent quantum efficiency (AQE) of CdS and CdS/UiO-66 composites with different weight ratios of CdS for photocatalytic H2 production. Cat. AQE (%) CdS/UiO-66(10) 0.64 CdS/UiO-66(20) 0.85 CdS/UiO-66(40) 0.72 CdS 0.19 The apparent quantum efficiency (AQE) was roughly evaluated under the following reaction as follows: A certain amount of the CdS/UiO-66(X) (with a fixed CdS amount of 80 mg) or 80 mg CdS was dispersed in 4 ml acetonitrile with 0.3 ml deionized water and 1 ml lactic acid. Light source: 300 W Xenon lamp irradiation with a monochromatic light filter (λ = 420 nm). The AQE is calculated as following equation: AQE = 2 the number of evolved H 2 molecules the number of incident photons S13

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