Supporting Information. Size-tunable Ni nanoparticles supported on surface-modified, cage-type mesoporous

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1 Supporting Information Size-tunable Ni nanoparticles supported on surface-modified, cage-type mesoporous silica as highly active catalysts for CO 2 hydrogenation Ching-Shiun Chen, a,b* Canggih Setya Budi, c Hung-Chi Wu, a Diganta Saikia, c and Hsien-Ming Kao c* a Center for General Education, Chang Gung University, 259, Wen-Hua 1 st Rd., Guishan Dist., Taoyuan City 33302, Taiwan, Republic of China. cschen@mail.cgu.edu.tw b Department of Pathology, Chang Gung Memorial Hospital, 5, Fusing St., Guishan Dist., Taoyuan City 33302, Taiwan, Republic of China. c Department of Chemistry, National Central University, Chung-Li, 32001, Taiwan, Republic of China.

2 Characterization methods 13 C and 29 Si solid-state NMR spectroscopy was conducted on a Varian-500 spectrometer under magic angle spinning (MAS) conditions. The presence of the carboxylic acid moiety was also probed by Fourier transform infrared spectroscopy (FT-IR, JASCO 4200 spectrometer). Zeta potential measurements were performed on a Malvern, Zetasizer Nano-ZS90 instrument. Powder X-ray diffraction (XRD) patterns were collected on two different sources: small angle regions were recorded on Wiggler-A beamline (λ = nm) provided by the National Synchrotron Radiation Research Center of Taiwan, and wide angle regions were measured on a Shimadzu diffractometer (Lab-X XRD 6000) with a monochromatic Cu K α radiation (λ = nm). The analysis of the N 2 adsorption-desorption isotherms, which were measured on a Micromeritics ASAP 2020 analyzer, determined the textural properties of the samples. The Brunauer-Emmett-Teller (BET) method was employed to obtain specific surface areas. The pore volume was determined from the volumes of N 2 adsorbed at P/P 0 = 0.95 or in the vicinity. The entrance and cage pore sizes were given by the analysis results of the desorption and adsorption branches of the isotherms, respectively, by the BJH (Barrett-Joyner-Halenda) method. The mesostructures of the samples were investigated by using transmission electron microscope (TEM, JEOL JEM2010) and ultrahigh resolution transmission electron

3 microscope (Ultra HRTEM, JEOL JEM-ARM200F). The Ni contents that were actually incorporated into S16C were determined by using inductively coupled plasma-atomic emission spectrometer (ICP-AES, Jarrell-Ash, ICAP 9000).

4 Table S1 Comparison for Ni surface and dispersion of 2 and Ni loading (wt%) Support Ni surface area (m 2 /g-cat) Dispersion (%) 5.6 SiO SiO SiO S16C S16C S16C

5 Table S2 Weisz-Prater criterion calculation for CO 2 and H 2 over Ni(21.7)@S16C and Ni(20)@SiO 2 catalysts Ni(21.7)@S16C Ni(20)@SiO 2 reactant 673 K 773 K 673 K 773 K CO H The Weisz-Prater criterion was calculated using the following equation: N W P RR = C D s 2 p eff R: reaction rate (mole s -1 cm -3 ) R p : the radius of Ni(21.7)@S16C and Ni(20)@SiO 2 particles (cm) through a 100-mesh and 60-mesh screen were estimated to be cm and cm, respectively C s : reactant concentration (mole cm -3 ) D eff : the effective diffusivity in pore of the catalyst (cm 2 s -1 ) The values of D eff are calculated from the equation: D eff ν d = 3 p ( ν : average velocity for molecule; d p : pore diameter of support) The pore diameters of SiO 2 and S16C are estimated to be 15 nm and 7 nm, respectively. Table S3 Comparison of TOF of CO 2 hydrogenation on Ni based catalysts

6 Catalyst Temperature ( o C) TOF (s -1 ) Reference 15 wt% Ni/Al 2 O wt% Ni/MSN wt% Ni/MCM wt% Ni/HY wt% Ni/Al 2 O Ni(5.9)@S16C this work Ni(14.2)@S16C this work Ni(21.7)@S16C this work

7 Table S4 Comparison of selectivity of CH 4 for CO 2 hydrogenation on Ni(x)@SBA-16 and Ni(x)@S16C catalysts at 673 K Ni loading (wt%) Support Conversion (%) Selectivity of CH 4 (%) 5.9 S16C S16C S16C SBA SBA SBA

8 Figure S1 (a) acid-base titration curve and (b) zeta potentials of the support S16C, (c) color change and (d) wide angle XRD patterns of the prepared as a function of ph.

9 Figure S2. Wide-angle XRD patterns of 2 as a function of the Ni loading. All catalysts were calcined in air and reduced in H 2 at 673 K for 5 h, respectively.

10 Figure S3. (A) 13 C CPMAS NMR of S16C, (B) 13 C NMR spectrum of the liquid CES in CDCl 3 solvent; (C) and (D) 29 Si MAS NMR spectra of SBA-16 and S16C, respectively.

11 Figure S4. FTIR spectra of (a) SBA-16, (b) (c) and (d)

12 Figure S5. XPS spectra of as a function of Ni loading.

13 Figure S6. Comparison of the conversion and product selectivity for CO 2 hydrogenation on the Ni(x)@S16C and Ni(x)@SiO 2 catalysts as a function of temperature in Figure 4: (A) overall CO 2 hydrogenation; (B) CO selectivity and (C) CH 4 selectivity. A H 2 /CO 2 stream with a 1:1 ratio at a total flow rate of 100 ml min -1 was passed over 5 mg of the catalysts.

14 Figure S7. Wide-angle XRD patterns of catalysts undergoing CO 2 hydrogenation for 48 h at 773 K.

15 Figure S8. Comparison of the CH 4 selectivity versus the reaction conversion on the Ni(x)@S16C catalysts.

16 Figure S9. TPD plots of (A) CO 2 and (B) CO desorbed from the Ni(x)@SiO 2 catalysts in a He stream with a 10 K min -1 heating rate. All CO 2 and CO adsorptions were performed in a pure 100 ml min -1 stream at atmospheric pressure and 298 K for 40 min.

17 Figure S10. TPH plots of CO 2 desorbed from the Ni(20)@SiO 2 catalysts in a 100 ml min -1 H 2 /He (20/80) stream with a 10 K min -1 heating rate. CO 2 adsorption was performed in a pure 100 ml min -1 CO 2 stream at atmospheric pressure and 298 K for 40 min.

18 Figure S11. Comparison of the reaction rates for CO 2 hydrogenation on Ni NPs deposited on pure silica SBA-16 without COOH groups and S16C with COOH groups.

19 Figure S12. (A) H 2 -TPR of impregnated Ni(x)@S16C as a function of Ni loading, where x = (a) 5.9, (b) 14.2, (c) 21.7 wt% and (d) calcined Ni(21.7)@S16C; (B) H 2 -TPR of Ni(x)@SBA-16 as a function of Ni loading, where x = (a) 5.8, (b) 12.9, and (c) 22.9 wt%.

20 Figure S13. Wide-angle XRD patterns of 2 as a function of the Ni loading. All impregnated samples were directly reduced in H 2 at 673 K for 5 h.

21 Figure S14. Comparison of the reaction rates for CO 2 hydrogenation on the Ni(x)@S16C and Ni(x)@SiO 2 catalysts as a function of temperature. The Ni(x)@SiO 2 catalysts were reduced in H 2 at 673 K for 5 h.