Supporting Information Hydrogen Storage in the Dehydrated Prussian Blue Analogues M 3 [Co(CN) 6 ] 2 (M = Mn, Fe, Co, Ni, Cu, Zn) Steven S. Kaye and Jeffrey R. Long* Dept. of Chemistry, University of California, Berkeley, CA 94720-1460 e-mail: jlong@cchem.berkeley.edu J. Am. Chem. Soc. S1
Experimental Details Synthesis of M 3 [Co(CN) 6 ] 2 nh 2 O (M = Mn, Fe, Co, Ni, Cu, Zn). The preparations employed involved slight modifications to a literature procedure. 1 A solution of K 3 [Co(CN) 6 ] (10 mmol in 100 ml deionized H 2 O) was added dropwise to a stirred solution of M(NO 3 ) 2 (18 mmol in 100 ml deinonized H 2 O). The resulting precipitate was allowed to anneal in the mother liquor for 24 h, then filtered, washing with 3 200 ml deinonized H 2 O. The precipitate was then dried in air to give M 3 [Co(CN) 6 ] 2 nh 2 O (M = Mn, Fe, Co, Ni, Cu, Zn) in quantitative yield. Anal. Calcd for K 0.07 Mn 2.96 [Co(CN) 6 ] 2 15H 2 O: K, 0.32; Co, 13.6; C, 16.64; H, 3.49; N, 19.41. Found: K, 0.33; Co, 13.7; C, 16.85; H, 3.17; N, 19.73. Anal. Calcd for K 0.08 Fe 2.96 [Co(CN) 6 ] 2 16H 2 O: K, 0.36; Co, 13.6; C, 16.59; H, 3.48; N, 19.35. Found: K, 0.37; Co, 14.0; C, 16.39; H, 3.40; N, 19.02. Anal. Calcd for K 0.05 Co 2.98 [Co(CN) 6 ] 2 16H 2 O: K, 0.22; Co, 33.4; C, 16.42; H, 3.45; N, 19.15. Found: K, 0.23; Co, 33.0; C, 16.11; H, 3.91; N, 18.78. Anal. Calcd for K 0.04 Ni 2.98 [Co(CN) 6 ] 2 15H 2 O: K, 0.18; Co, 13.4; C, 16.44; H, 3.45; N, 19.17. Found: K, 0.16; Co, 13.3; C, 16.13; H, 3.32; N, 19.03. Anal. Calcd for K 0.03 Cu 2.99 [Co(CN) 6 ] 2 15H 2 O: K, 0.13; Co, 13.2; C, 16.17; H, 3.39; N, 18.86. Found: K, 0.15; Co, 13.1; C, 16.34; H, 3.02; N, 19.22. Anal. Calcd for K 0.1 Zn 2.95 [Co(CN) 6 ] 2 15H 2 O: K, 0.44; Co, 13.1; C, 16.06; H, 3.37; N, 18.73. Found: K, 0.44; Co, 12.9; C, 16.37; H, 3.84; N, 19.01. The powder X- ray diffraction pattern of all compounds matched that of the pattern simulated from the corresponding single crystal structure of the M 3 [Co(CN) 6 ] 2 nh 2 O compound with the Prussian blue structure. Gas Sorption Measurements. Sample tubes of a known weight were loaded with 200-400 mg of sample and sealed using a transeal. Samples were degassed at 95 C for 48-60 h on a Micromeritics ASAP 2020 analyzer until the outgas rate was no more than 1 mtorr/s. The degassed sample and sample tube were weighed precisely and then transferred back to the analyzer (with the transeal preventing exposure of the sample to air after degassing). The outgas rate was again confirmed to be no more than 1 mtorr/s. Measurements were performed either at 77 K in a liquid nitrogen bath, or at 87 K in a liquid argon bath. (1) De Robertis, A.; Bellomo, A.; De Marco, D. Talanta, 1976, 23, 732-4. S2
Analysis of Gas Sorption Isotherms. Dihydrogen sorption isotherms were fitted to the Langmuir-Freundlich equation instead of the more commonly used Langmuir equation. The Langmuir-Freundlich equation gives an accurate fit over a larger pressure range, resulting in a more accurate prediction of the quantity of dihydrogen sorbed at saturation. Surface areas were determined by fitting the argon sorption isotherm of a compound to the BET equation. Enthalpies of adsorption were calculated using a variant of the Clausius-Clapeyron equation: P ln( P 1 2 T 2 -T 1 ) = DHads * where P n = Pressure for isotherm n R* T 1* T 2 T n = Temperature for isotherm n. R = 8.315 J * K -1 * mol -1 which can be used to calculate the enthalpy of adsorption for a given quantity of dihydrogen adsorbed. Pressure as a function of the amount adsorbed was determined using the Langmuir-Freundlich fit for each isotherm: Q Q m (1/ t) B * P = where Q = moles adsorbed (1/ t) 1+ B * P Q m = moles adsorbed at saturation P = pressure B and t = constants. This rearranges to: Ê Q ˆ Á Qm P = Á Á Q Á B - B * Ë Qm t Which when substituted into the equation above gives: S3
S4 ˆ Á Á Á Á Ë Ê - ˆ Á Á Á Á Ë Ê - - = D 2 2 2 2 2 1 1 1 1 1 2 2 1 * * *ln * * m m m m ads Q Q B B Q Q Q Q B B Q Q T T T T R H Other Physical Measurements. Carbon, hydrogen and nitrogen analyses were obtained from the Microanalytical Laboratory of the University of California, Berkeley. Potassium and cobalt analyses were obtained from Huffman Laboratories. Powder X-ray diffraction data was collected using Cu Ka (l = 1.5406 Å) radiation on a Siemens D5000 diffractometer. Thermogravimetric analyses were carried out at a ramp rate of 0.25 C/min under a dinitrogen atmosphere, using a TA Instruments TGA 2950.
Figure S1. X-ray powder diffraction data for M 3 [Co(CN) 6 ] 2 15H 2 O. The broad peak at 13 is due to scattering from the sample holder. S5
Figure S2. X-ray powder diffraction data for Fe 3 [Co(CN) 6 ] 2 16H 2 O. The broad peak at 13 is due to scattering from the sample holder. S6
Figure S3. X-ray powder diffraction data for Co 3 [Co(CN) 6 ] 2 16H 2 O. The broad peak at 13 is due to scattering from the sample holder. S7
Figure S4. X-ray powder diffraction data for Ni 3 [Co(CN) 6 ] 2 15H 2 O. The broad peak at 13 is due to scattering from the sample holder. S8
Figure S5. X-ray powder diffraction data for Cu 3 [Co(CN) 6 ] 2 15H 2 O. The broad peak at 13 is due to scattering from the sample holder. S9
Figure S6. X-ray powder diffraction data for Zn 3 [Co(CN) 6 ] 2 15H 2 O. The broad peak at 13 is due to scattering from the sample holder. S10
Figure S7. Thermogravimetric analysis showing the weight loss in Mn 3 [Co(CN) 6 ] 2 15H 2 O, with temperature increasing at a rate of 0.25 C/min. S11
Figure S8. Thermogravimetric analysis showing the weight loss in Fe 3 [Co(CN) 6 ] 2 16H 2 O, with temperature increasing at a rate of 0.25 C/min. S12
Figure S9. Thermogravimetric analysis showing the weight loss in Co 3 [Co(CN) 6 ] 2 16H 2 O, with temperature increasing at a rate of 0.25 C/min. S13
Figure S10. Thermogravimetric analysis showing the weight loss in Ni 3 [Co(CN) 6 ] 2 15H 2 O, with temperature increasing at a rate of 0.25 C/min. S14
Figure S11. Thermogravimetric Analysis showing the weight loss in Cu 3 [Co(CN) 6 ] 2 15H 2 O, with temperature increasing at a rate of 0.25 C/min. S15
Figure S12. Thermogravimetric Analysis showing the weight loss in Zn 3 [Co(CN) 6 ] 2 15H 2 O, with temperature increasing at a rate of 0.25 C/min. S16
Figure S13. Argon sorption isotherm for Mn 3 [Co(CN) 6 ] 2 at 87 K. S17
Figure S14. Argon sorption isotherm for Fe 3 [Co(CN) 6 ] 2 at 87 K. S18
Figure S15. Argon sorption isotherm for Co 3 [Co(CN) 6 ] 2 at 87 K. S19
Figure S16. Argon sorption isotherm for Ni 3 [Co(CN) 6 ] 2 at 87 K. S20
Figure S17. Argon sorption isotherm for Cu 3 [Co(CN) 6 ] 2 at 87 K. S21
Figure S18. Argon sorption isotherm for Zn 3 [Co(CN) 6 ] 2 at 87 K. S22
Figure S19. Dihydrogen sorption isotherms for Mn 3 [Co(CN) 6 ] 2 at 77 K (blue circles) and 87 K (red squares). The solid lines represent the best fit to the data using the Langmuir-Freundlich equation, as described above. Extrapolation of the fit gives a prediction of 2.1 wt. % H 2 adsorbed at saturation. S23
Figure S20. Dihydrogen sorption isotherms for Fe 3 [Co(CN) 6 ] 2 at 77 K (blue circles) and 87 K (red squares). The solid lines represent the best fit to the data using the Langmuir- Freundlich equation, as described above. Extrapolation of the fit gives a prediction of 1.8 wt. % H 2 adsorbed at saturation. S24
Figure S21. Dihydrogen sorption isotherms for Co 3 [Co(CN) 6 ] 2 at 77 K (blue circles) and 87 K (red squares). The solid lines represent the best fit to the data using the Langmuir- Freundlich equation, as described above. Extrapolation of the fit gives a prediction of 1.9 wt. % H 2 adsorbed at saturation. S25
Figure S22. Dihydrogen sorption isotherms for Ni 3 [Co(CN) 6 ] 2 at 77 K (blue circles) and 87 K (red squares). The solid lines represent the best fit to the data using the Langmuir- Freundlich equation, as described above. Extrapolation of the fit gives a prediction of 1.7 wt. % H 2 adsorbed at saturation. S26
Figure S23. Dihydrogen sorption isotherms for Cu 3 [Co(CN) 6 ] 2 at 77 K (blue circles) and 87 K (red squares). The solid lines represent the best fit to the data using the Langmuir- Freundlich equation, as described above. Extrapolation of the fit gives a prediction of 2.1 wt. % H 2 adsorbed at saturation. S27
Figure S24. Dihydrogen sorption isotherms for Zn 3 [Co(CN) 6 ] 2 at 77 K (blue circles) and 87 K (red squares). The solid lines represent the best fit to the data using the Langmuir- Freundlich equation, as described above. Extrapolation of the fit gives a prediction of 1.8 wt. % H 2 adsorbed at saturation. S28
Figure S25. Dihydrogen sorption isotherms for Zn 4 O(1,4-benzenediarboxylate) 3 at 77 K (blue circles) and 87 K (red squares). The solid lines represent the best fit to the data using the Langmuir-Freundlich equation, as described above. Extrapolation of the fit gives a prediction of 4.8 wt. % H 2 adsorbed at saturation. S29
Figure S26. Dihydrogen sorption by Cu 3 [Co(CN) 6 ] 2 at 1 atm. and 77 K as a function of the number of adsorption/desorption cycles. S30