Broadly Hysteretic H 2 Adsorption in the Microporous Metal-Organic Framework Co(1,4-benzenedipyrazolate)

Transcription

1 Supporting Information for: Broadly Hysteretic H 2 Adsorption in the Microporous Metal-Organic Framework Co(1,4-benzenedipyrazolate) Hye Jin Choi, Mircea Dinca, and Jeffrey R. Long* Department of Chemistry, University of California, Berkeley, California J. Am. Chem. Soc. S-1

2 Experimental Details Water was distilled and deionized prior to use. All other reagents were obtained from commercial vendors, and were used without further purification. Synthesis of 1,4-benzenedi(4 -pyrazolyl) (H 2 BDP). 1 Under a nitrogen atmosphere, 7.0 ml of phosphorus oxychloride (7.0 ml) was added to 7.0 ml of anhydrous DMF in a three-neck round-bottom flask and the mixture was chilled in an ice bath for 10 min. A solution of p- phenylenediacetic acid (2.0 g, mol) in 10 ml of DMF was added, and the reaction mixture was heated at 80 C for 18 h. While still hot, the resultant dark solution was poured into ca. 200 ml of ice water, and a solution of NaClO 4 (9.5 g, mol) in 100 ml of water was added to afford a pale-yellow precipitate. The solid was collected by filtration, washed with successive aliquots of water (5 20 ml), methanol (3 20 ml), and ether (3 20 ml), and dried under reduced pressure to yield 4.9 g (92%) of 1,4-benzenebis(2 -(1,3 -dimethylamino)- trimethinium))diperchlorate (C 20 H 32 O 8 N 4 Cl 2, A). 2 IR (solid, ATR): 2936 (ν C-H, w), 1582 (ν C=N, vs), 1489 (w), 1452 (w), 1393 (m), 1287 (m), 1211 (m), 1078 (vs), 975 (m), 761 (w), 622 (m), 586 (w) cm -1. Anal. Calcd for C 20 H 32 O 8 N 4 Cl 2 : C, 45.54; H, 6.07; N, Found: C, 45.25; H, 6.29; N, A 50-mL aliquot of 0.01 M NaOH was added to a suspension of A (5.0 g, 9.5 mmol) in 150 ml of water, and the solution was stirred and heated at 70 C for 1 h. The resulting colorless solution was titrated with a 1.2 M aqueous HCl solution until the ph of the solution was 3. Hydrazine monohydrate (4.0 ml, 79 mmol) was added and the mixture was heated at 55 C for 1 h to give a pale yellow precipitate. The solid was collected by filtration, washed with successive aliquots of water (3 50 ml), and dried in air to afford 0.90 g (45%) of product. IR (solid, ATR): ν N-H 3135, 3111, 3079, ν C-H 2929, 2855, 2677, ν C=N 1581 cm H NMR (DMSOd 6 ): δ (s, br, 2H), 8.16 (s, br, 2H), 7.96 (s, br, 2H), 7.58 (s, 4H) ppm. 13 C NMR (DMSOd 6 ): δ 131, 126, 121 ppm (tertiary C). MS(EI + ): m/z = 210 (M +, 100 %). Anal. Calcd: C, 68.56; H, 4.79; N, Found: C, 68.28; H, 4.79; N, This compound is soluble in DMSO or hot DMF, and is insoluble in other common organic solvents. 1 For an alternative, related preparation, see: Lozan, V.; Solntsev, P. Y.; Leibeling, G.; Domasevitch, K. V.; Kersting, B. Eur. J. Inorg. Chem. 2007, Arnold, Z. Coll. Czechoslov. Chem. Commun. 1965, 30, S-2

3 Synthesis of Co(BDP) 2DEF H 2 O. A borosilicate tube (1.2 cm o.d. 15 cm length) was charged with Co(CF 3 SO 3 ) 2 (120 mg, 0.34 mmol), H 2 BDP (60 mg, 0.29 mmol), and 2.0 ml of N,N -diethylformamide (DEF). The reaction mixture was degassed by the freeze-pump-thaw method (5 cycles), and the tube was sealed under reduced pressure. The tube was heated in an oil bath at 130 C for 6 days to afford a purple microcrystalline solid. Upon cooling to room temperature, the tube was broken open in air and the solid was immediately collected by filtration. The solid was then washed with successive aliquots of DEF (5 10 ml) and dried under reduced pressure for 30 min to afford 0.13 g (95%) of product. The compound was stored under an atmosphere of DEF vapor. IR (solid, ATR): ν C=C 1576, ν C=N 1433, 1399, ν C=O 1658 cm - 1. Anal. Calcd for C 22 H 32 CoN 6 O 3 : C, 54.21; H, 6.62; N, Found: C, 54.18; H, 5.95; N, Single crystals suitable for X-ray analysis were obtained from a smaller-scale reaction employing a borosilicate tube (0.7 cm o.d. 8 cm length) charged with Co(CF 3 SO 3 ) 2 (30 mg, mmol), H 2 BDP (15 mg, mmol), and DEF (0.4 ml). After degassing and sealing, the tube was heated in a programmable furnace: the temperature was increased at a rate of 0.1 C/min to 130 C, which was maintained for 4 days prior to cooling at a rate of 0.1 o C/min to room temperature. Low-Pressure Gas Adsorption Measurements. Gas adsorption isotherms for pressures in the range bar were measured by a volumetric method using a Micromeritics ASAP2020 instrument. Crystals of Co(BDP) 2DEF H 2 O were transferred to a preweighed analysis tube, which was capped with a Transeal and evacuated by heating at 170 C under dynamic vacuum until an outgas rate of less than 2 mtorr/min (0.27 Pa/min) was achieved (ca. two days). The evacuated analysis tube containing the degassed sample of Co(BDP) was then carefully transferred to an electronic balance and weighed again to determine the mass of sample (62.8 mg). The tube was then transferred back to the analysis port of the gas adsorption instrument. The outgas rate was again confirmed to be less than 2 mtorr/min (0.27 Pa/min). For all isotherms, warm and cold free space correction measurements were performed using ultra-highpurity He gas (UHP grade 5.0, % purity); N 2, O 2, and H 2 isotherms at 77 and 87 K were measured in liquid nitrogen and liquid argon baths, respectively, using UHP-grade gas sources. Oil-free vacuum pumps and oil-free pressure regulators were used for all measurements to S-3

4 prevent contamination of the samples during the evacuation process or of the feed gases during the isotherm measurements. High-Pressure H 2 Adsorption Measurements and Data Analysis. Crystals Co(BDP) 2DEF H 2 O were degassed by the method described in the previous section. The sample was then loaded into the sample holder under a nitrogen atmosphere. Excess adsorption of H 2 was measured using an automated Sieverts apparatus (PCT-Pro 2000 from Hy-Energy LLC) over a pressure range of 0-90 bar. At least 200 mg of adsorbent was used in each experiment, and UHP-grade hydrogen and helium (99.999% purity) were used for all measurements. Measurements at 77 and 87 K were performed by submerging the sample in liquid nitrogen or liquid argon, respectively, while measurements at 50 and 65 K were performed by using the CryoPro workstation with a PID temperature controller (from Cryo-Con) attached to the sorption analyzer. Liquid helium was used as the cryogen in the cryostat. The volume of the sample holder and the connecting gas manifold were determined prior to sample measurement using He at 298 K, and at all of the temperatures used for the measurements (50, 65, 77, 82, and 87 K). Helium was used to determine the dead space volume correction for a non-porous sample of known volume; this correction accounted for the change in effective sample volume observed when cooling the sample holder from room temperature to low temperature. The adsorbent was then introduced into the sample holder and He gas was used to determine the volume of the sample at room temperature. Since He gas penetrates the pores of the sample without being adsorbed onto the surface, the volume measured with He corresponds to the volume of the framework walls, also referred to as the framework skeleton. Consequently, the skeletal density of the material, d sk, can be obtained from the following expression. d sk = m/v sk (1) Here, m is the sample mass expressed in g and V sk is the sample volume in cm 3, as determined using He expansion at room temperature. In order to obtain an accurate assessment of the value of the skeletal density, the volume of the sample, V sk, was measured 20 times and the average of these was used as the final value. High-Pressure H 2 Adsorption Kinetics Measurements and Data Analysis. A degassed sample of Co(BDP) was prepared as described above, loaded into the sample holder under nitrogen atmosphere, and installed in the high-pressure PCT-Pro 2000 instrument. The desired S-4

5 temperatures (77, 79, 82, and 87 K) were achieved by the method described above employing the CryoPro workstation with PID temperature controller. For a typical measurement, high pressure H 2 (67-77 bar) was quickly loaded into the sample chamber, within a second for each temperature measured, and the time-dependent increase of the adsorbed H 2 amount was monitored until equilibrium was reached. Each kinetics curve was normalized and fit to the double exponential model N t /N e = A 1 (1 e k t 1 ) + A 2 (1 e k t 2 ) (2) where N t and N e represent the amount of at time t and at equilibrium, respectively, k 1 and k 2 are the kinetic rate constants corresponding to the diffusion at the pore entrance and along the pore cavities, respectively, and A 1 and A 2 are the relative contributions of the two barriers controlling the overall adsorption, with A 1 + A 2 = 1. Due to substantial changes in framework structure during the measurements, the parameters A 1 and A 2 were not fixed and were treated as variables. In particular, A 1 would be significantly more affected by the opening of the poreentrance during the adsorption process. The resultant fit parameters of k 1, k 2, A 1, and A 2 with standard errors are listed in Table S7. X-ray Structure Determination. A single crystal of Co(BDP) 2DEF H 2 O was coated in Paratone-N oil, attached to a Kapton loop, quickly transferred to a Bruker Platinum 200 Instrument at the Advanced Light Source at the Lawrence Berkeley National Laboratory, and cooled in a stream of nitrogen. Preliminary cell data were collected to give a unit cell consistent with the tetragonal Laue group, and the unit cell parameters were later refined against all data. A full hemisphere of data was collected, and the crystal didn t show significant decay during data collection. Data were integrated and corrected for Lorentz and polarization effects using SAINT 7.07b and were corrected for absorption effects using SADABS Crystal and refinement parameters are listed in Table S1. Space group assignments were based upon systematic absences, E statistics, and successful refinement of the structures. The structure was solved by direct methods and expanded through successive difference Fourier maps. It was refined against all data using the SHELXTL 5.0 software package. The refined Flack parameter suggested twinning, and a twin component was therefore included with the twinning law of The twin components, including a racemic mixture, refined to a ratio of 0.207:0.277:0.296:0.220, and their implementation lowered R 1 from 0.18 to Thermal S-5

6 parameters for all non-hydrogen atoms pertaining to the framework skeleton were refined anisotropically. Thermal parameters for partially-occupied sites associated with disordered C, N, and O atoms pertaining to solvent molecules were refined isotropically. Hydrogen atoms associated with disordered atoms were not included in the structural refinements. All other hydrogen atoms were assigned to ideal positions and refined using a riding model with an isotropic thermal parameter 1.2 times that of the attached atom (1.5 times for methyl hydrogens). Disorder in bond distances and angles of phenyl ring and pyrazole ring of the ligand molecule were restrained by FLAT and DFIX commands. Due to disorder, the C-N, C-C, and C=O distances in two DEF molecules in the structure were constrained to idealized lengths of 1.47, 1.54 and 1.25 Å, respectively. Other Physical Measurements. Infrared spectra were collected on a Nicolet Avatar 360 FTIR spectrometer equipped with an attenuated total reflectance accessory (ATR). Carbon, hydrogen, and nitrogen analyses were obtained from the Microanalytical Laboratory of the University of California, Berkeley. Powder X-ray diffraction data was collected using Cu Kα (λ = Å) radiation on a Bruker D8 Advance diffractometer. Thermogravimetric analyses were carried out at a ramp rate of 1 C/min in a nitrogen flow with a TA Instruments TGA Q5000 V3.1 Build 246. Acknowledgment. This research was funded by General Motors Corporation. We thank Dr. A. Dailly and Dr. E. Poirier for experimental assistance, and Dr. S. Horike and Dr. F. J. Hollander for helpful discussions. A portion of this research was conducted at the Advanced Light Source facility at the Lawrence Berkeley National Laboratory, which is operated by the DOE under contract DE-AC03-76SF S-6

7 Table S1. Crystallographic Data for Co(BDP) 2DEF H 2 O. Identification Co(BDP) 2DEF H 2 O Formula C 22H 32CoN 6O 3 FW T, K 193(2) Wavelength, Å Crystal system, space group Orthorhombic, P222(1) Z 4 a, Å (2) b, Å (0) c, Å (2) V, Å (5) d calc, g/cm Adsorption coefficient, mm F(000) 1028 Crystal size, mm Theta range for data collection Index range -14 h 14, -14 k 14, -15 l 15 Reflections collected 3515 Independent reflections 3100 [R(int) = ] Data/restrains/parameters 3515 / 24 /221 GOF on F Largest diff. peak and hole, e Å and R 1 (wr 2) a, [I>2sigma(I)] (0.2116) R 1 (wr 2) a, all data (0.2211) a R 1 = Σ Fo - Fc /Σ Fo, wr 2 = {Σ[w(Fo 2 -Fc 2 ) 2 ]/Σ[w(Fo 2 ) 2 ]} 1/2. S-7

8 Table S2. Adsorption and Desorption Data for N 2 Uptake in Co(BDP). T = 77 K T = 87 K P/P 0 N 2 adsorbed (cm 3 /g) P/P 0 N 2 adsorbed (cm 3 /g) S-8

9 Table S2 (continued) T = 77 K T = 87 K P/P 0 N 2 adsorbed (cm 3 /g) P/P 0 N 2 adsorbed (cm 3 /g) S-9

10 Table S2 (continued) T = 77 K T = 87 K P/P 0 N 2 adsorbed (cm 3 /g) P/P 0 N 2 adsorbed (cm 3 /g) S-10

11 Table S3. Adsorption and Desorption Data for H 2 Uptake in Co(BDP) at high pressure at 50 and 65 K. T = 50 K Pressure (bar) Excess H 2 adsorbed (wt %) T = 65 K Pressure (bar) Excess H 2 adsorbed (wt %) S-11

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13 Table S4. Adsorption and Desorption Data for H 2 Uptake in Co(BDP) at High Pressure and at 77 and 87 K. T = 77 K Pressure (bar) Excess H 2 adsorbed (wt %) T = 87 K Pressure (bar) Excess H 2 adsorbed (wt %) S-13

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15 Table S5. Adsorption and Desorption Data for H 2 and O 2 Uptake in Co(BDP) at Low Pressures. T = 77 K T = 77 K Pressure (mmhg) (cm 3 /g) Pressure (mmhg) O 2 adsorbed (cm 3 /g) S-15

16 Table S6. Adsorption Kinetics Data for H 2 Uptake in Co(BDP). T = 77 K T = 79 K T = 82 K T = 87 K time (s) (a.u.) S-16

17 Table S6 (continued) T = 77 K T = 79 K T = 82 K T = 87 K time (s) (a.u.) S-17

18 Table S6 (continued) T = 77 K T = 79 K T = 82 K T = 87 K time (s) (a.u.) S-18

19 Table S6 (continued) T = 77 K T = 79 K T = 82 K T = 87 K time (s) (a.u.) S-19

20 Table S7. Kinetics rate constants (k 1, and k 2 ) and their corresponding contribution coefficients (A 1 and A 2 ) estimated by fitting the adsorption kinetic profiles to double exponential model. T (K) A 1 k 1 (s -1 ) A 2 k 2 (s -1 ) (4) (2) 0.546(4) (2) (5) (2) 0.529(5) (3) (4) (1) 0.453(4) (3) (5) (1) 0.349(5) (6) S-20

21 Figure S1. Thermogravimetric analysis data for 1, as measured using a ramp rate of 1.0 C/min. S-21

22 Figure S2. Adsorption isotherms for O 2 in 1d at 77 and 87 K, and for H 2 in 1d at 77 K. Filled and open symbols represent adsorption and desorption data, respectively. S-22

23 Figure S3. Powder X-ray diffraction patterns for the crystallographic simulation (black), pulverized crystals of 1 (blue), the completely desolvated material 1d obtained upon evacuation at 170 C for 2 days (green), and the resolvated material obtained upon exposure of 1d to DEF for 3 min (red). S-23