Supporting Information

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1 Supporting Information Formation of Hierarchical In 2 S 3 -CdIn 2 S 4 Heterostructured Nanotubes for Efficient and Stable Visible Light CO 2 Reduction Sibo Wang, Bu Yuan Guan, Yan Lu, and Xiong Wen (David) Lou* School of Chemical and Biomedical Engineering, Nanyang Technological University, 62 Nanyang Drive, Singapore , Singapore * Corresponding author. xwlou@ntu.edu.sg Experimental details Synthesis of MIL-68 hexagonal prisms: The MIL-68 hexagonal prisms were synthesized according to a reported method with some modifications. 1 Typically, 4.5 mg of In(NO3)3 xh2o (Sigma-Aldrich) and 5.5 mg of 1,4-benzenedicarboxylic acid (H2BDC) were dissolved in 2 ml of DMF and stirred for 5 min. Then, the resultant solution was placed in an oil bath at 120 C for 30 min. After the reaction, the white precipitate was filtrated and washed with ethanol three times. Synthesis of hierarchical In2S3 nanotubes: The obtained MIL-68 hexagonal prisms were added into 40 ml of an ethanol solution containing 200 mg of thiourea, and stirred for 2 min. Then, the resultant mixture was transferred into a Teflon-lined autoclave (80 ml in capacity) and maintained at 180 C for 3 h. After cooling down to room temperature, the yellow precipitate was filtrated and washed with ethanol and H2O three times. Synthesis of hierarchical In2S3-CdIn2S4 and CdIn2S4 nanotubes: Conversion of In2S3 nanotubes to S1

2 In2S3-CdIn2S4 and CdIn2S4 nanotubes was realized via an efficient cation exchange method. The In2S3 nanotubes were dispersed in 9 ml of H2O, followed by the addition of 1 ml of CdCl2 solution (0.1 M). The resultant mixture was stirred for 2 min and maintained at 60 C for 5, 10 and 15 min, respectively. Afterwards, the obtained yellow precipitates were filtrated, washed with ethanol and H2O, and died in vacuum at 60 C for 12 h. The products obtained were designated as In2S3-CdIn2S4-5, In2S3- CdIn2S4-10, and CdIn2S4, respectively. Materials characterization. The morphology and structure of the samples were examined by fieldemission scanning electron microscope (FESEM; JEOL-6700) and transmission electron microscope (TEM; JEOL, JEM-2010). The crystal phases of the samples were analyzed by X-ray diffraction (XRD) on a Bruker D2 Phaser X-Ray Diffractometer with Ni filtered Cu Kα radiation (λ = Å) at a voltage of 30 kv and a current of 10 ma. The compositions of the samples were analyzed by energy-dispersive X-ray spectroscope (EDX) attached to the FESEM instrument. Elemental mapping images were recorded using EDX spectroscope attached to TEM (JEOL, JEM-2100F). N2 and CO2 adsorption isotherms were collected on an ASAP2020M apparatus. The samples were degassed in vacuum at 120 C for 6 h, and then measured at -77 K and 0 C to determine N2 and CO2 adsorption, respectively. UV-vis diffuse reflectance spectra (DRS) were obtained using a Varian Cary 500 UVvis-NIR spectrometer equipped with an integrating sphere and BaSO4 was used as a reference. Photoluminescence (PL) spectra were acquired on Edinburgh Analytical Instruments FL/FSTCSPC920 coupled with a time-correlated single-photo-counting system at room temperature. Mott-Schottky measurements were performed on a Zenuium electrochemical workstation (Zahner Co.) using a conventional three electrodes cell with Pt plate and Ag/AgCl electrode as the counter electrode and reference electrode, respectively. For the Mott-Schottky experiments, the potential S2

3 ranged from to 0.1 V (vs. Ag/AgCl), and the frequency were 0.5, 1.0, and 1.5 khz. Prior to all measurements, the electrolyte (0.2 M Na2SO4 aqueous solution) was purged with N2. An Agilent 7820A gas chromatograph (GC) equipped with a thermal conductivity detector (TCD) and a packed column (TDX-01) was utilized to analyze and quantify the gases produced from the CO2 photoreduction system with Ar as the carrier gas. An HP 5973 gas chromatography-mass spectrometer (GC-MS) was employed to analyze the gaseous products generated from the 13 CO2 (97% enriched) isotopic experiment and to determine whether other potential products were generated in the liquid phase. Photocatalytic CO2 reduction. In the typical photocatalytic CO2 reduction reaction, 4 mg of photocatalysts, 15 mg of bipyridine (bpy), 2 μmol of CoCl2, 1 ml of triethanolamine (TEOA), 2 ml of H2O and 3 ml of acetonitrile (MeCN) were added into an 80 ml reactor. Then, high purity CO2 was introduced into the reactor with a partial pressure of 1 atm. A 300W Xe lamp with a 400 nm cutoff filter was used as the light source. The temperature of the reaction system was kept at 30 C. During the photocatalytic process, the reaction system was vigorously stirred with a magnetic stirrer. After the reaction, the generated products were quantified by an Agilent 7820A gas chromatograph. S3

4 Figure S1. XRD pattern of MIL-68 hexagonal prisms. Figure S2. XRD pattern of In2S3 nanotubes. S4

5 Figure S3. EDX spectrum of In2S3 nanotubes. Figure S4. EDX spectrum of In2S3-CdIn2S4-5 nanotubes. S5

6 Figure S5. (a,b) XRD patterns of In2S3-CdIn2S4-5 and In2S3-CdIn2S4-10 nanotubes. Figure S6. EDX spectrum of In2S3-CdIn2S4-10 nanotubes. S6

7 Figure S7. EDX spectrum of CdIn2S4 nanotubes. Figure S8. XRD pattern of CdIn2S4 nanotubes. S7

8 Figure S9. FESEM images of (a,b) In2S3-CdIn2S4-5 and (c,d) CdIn2S4 nanotubes. Figure S10. TEM images of (a,b) In2S3-CdIn2S4-5 and (c,d) CdIn2S4 nanotubes. S8

9 Figure S11. High-resolution TEM image of In2S3-CdIn2S4-10 nanotubes. Figure S12. DRS of In2S3, In2S3-CdIn2S4-5, In2S3-CdIn2S4-10 and CdIn2S4. S9

10 Figure S13. Tauc plots of In2S3, In2S3-CdIn2S4-5, In2S3-CdIn2S4-10 and CdIn2S4. Figure S14. Mott-Schottky plots of (a) In2S3, (b) In2S3-CdIn2S4-5, (c) In2S3-CdIn2S4-10, and (d) CdIn2S4. S10

11 Figure S15. N2 adsorption isotherms of In2S3-CdIn2S4-10. Figure S16. CO2 sorption isotherms of In2S3-CdIn2S4-10 at 0 C S11

12 Figure S17. PL spectra of In2S3, In2S3-CdIn2S4-5, In2S3-CdIn2S4-10 and CdIn2S4. Figure S18. Transient photocurrent response of In2S3, In2S3-CdIn2S4-5, In2S3-CdIn2S4-10 and CdIn2S4. S12

13 Figure S19. XRD patterns of In2S4-CdIn2S4-10 before and after photocatalytic CO2 reduction reactions. Figure S20. (a,b) FESEM images of In2S3-CdIn2S4-10 nanotubes after photocatalytic CO2 reduction reactions. S13

14 Table S1. Comparison of the performance of In2S3-CdIn2S4-10 catalyzed CO2 photoreduction system with that of some noble-metal-containing systems. Catalyst Photosensitizer Cocatalyst Sacrificial agent Major product evolution rate μmol h -1 g -1 Ref. In 2 S 3 -CdIn 2 S 4-10 / Co(bpy) 3 2+ N-Ta 2 O 5 [Ru(dcbpy) 2 (CO) 2 ] 2+a / SrTiO 3 /TiO 2 / Au-Cu 2+ Co 3 O 4 Ru(bpy) 3 RuRu /mpg-c 3 N 4 b RuRu /NS-C 3 N 4 c / / Ag / Ag UiO-66/CNNS d / / NH 2 -MIL-125(Ti) / / PCN-222 / / a dcbpy = 4,4 -dicarboxy-2,2 -bipyridine TEOA CO: 825 This work TEOA HCOOH: 70 2 N 2 H 4 H 2 O hydrocarbon: TEOA CO: EDTA 2Na HCOO - : EDTA 2Na COOH - : TEOA CO: TEOA COOH - : 40 8 TEOA COOH - : b RuRu = a Ru(II) binuclear complex; mpg-c 3 N 4 = mesoporous graphitic carbon nitride. c NS-C 3 N 4 = carbon nitride nanosheets. d CNNS = carbon nitride nanosheets. Supplementary References (1) Cho, W.; Lee, H. J.; Oh, M. J. Am. Chem. Soc. 2008, 130, (2) Sato, S.; Morikawa, T.; Saeki, S.; Kajino, T.; Motohiro, T. Angew. Chem. Int. Ed. 2010, 49, (3) Kang, Q.; Wang, T.; Li, P.; Liu, L.; Chang, K.; Li, M.; Ye, J. Angew. Chem. Int. Ed. 2015, 54, 841. (4) Gao, C.; Meng, Q.; Zhao, K.; Yin, H.; Wang, D.; Guo, J.; Zhao, S.; Chang, L.; He, M.; Li, Q.; Zhao, H.; Huang, X.; Guo, Y.; Tang, Z. Adv. Mater. 2016, 28, (5) Kuriki, R.; Matsunaga, H.; Nakashima, T.; Wada, K.; Yamakata, A.; Ishitani, O.; Maeda, K. J. Am. Chem. Soc. 2016, 138, (6) Kuriki, R.; Yamamoto, M.; Higuchi, K.; Yamamoto, Y.; Akatsuka, M.; Lu, D.; Yagi, S.; Yoshida, T.; Ishitani, O.; Maeda, K. Angew. Chem. Int. Ed. 2017, 56, S14

15 (7) Shi, L.; Wang, T.; Zhang, H.; Chang, K.; Ye, J. Adv. Funct. Mater. 2015, 25, (8) Fu, Y.; Sun, D.; Chen, Y.; Huang, R.; Ding, Z.; Fu, X.; Li, Z. Angew. Chem. Int. Ed. 2012, 51, (9) Xu, H. Q.; Hu, J.; Wang, D.; Li, Z.; Zhang, Q.; Luo, Y.; Yu, S. H.; Jiang, H. L. J. Am. Chem. Soc. 2015, 137, S15