Thermal Conductivity of Covalent Organic Frameworks as a Function of Their Pore Size

Transcription

1 Thermal Conductivity of Covalent Organic Frameworks as a Function of Their Pore Size Sunny K. S. Freitas a ; Raquel S. Borges b ; Claudia Merlini c, Guilherme M. O. Barra d, Pierre M. Esteves a, * a. Instituto de Química, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos, 149, CT, A-622, Cid. Univ., Rio de Janeiro, , RJ Brazil b. FMC Technologies, Rio de Janeiro, Brazil c. Mechanical Engineering Department, Federal University of Santa Catarina, Admar Gonzaga Avenue, 1346, , Florianópolis, SC Brazil d. Engineering Department, Federal University of Santa Catarina, Blumenau, SC, Brazil Supporting Information Powder X-ray diffraction (XRD) patterns were recorded in a Shimadzu XRD7000 diffractometer, using Cu-Kα radiation with a Δ2θ=0.02 in the 5 to 90 2θ range. Phase identification in the recorded patterns was carried out by using the Hanawalt method and the PDF-2002 and ICSD-2008 databases. The infrared spectra (FTIR) in the cm 1 region were recorded in samples prepared as diluted KBr pellets using a FTLA-2000 spectrometer. 13 C and CP MAS NMR spectra were collected on a 9.4 T WB Bruker Avance III spectrometer operating at Larmor frequencies of MHz (for 13 C) and 3.2 mm double-resonance MAS probe was employed. Samples were spun in ZrO 2 rotors and registered at room temperature. High resolution spectra were recorded using CP/MAS method (cross-polarization/ magic angle spinning) at 10 KHz. Samples were referenced to glycine (C=O, ppm vs. TMS). Acquisitions were performed using CP.ramp.100 pulse sequence using 4.5 us proton 90 o degree pulse and recycle delay of 4 s. All spectra were recorded 3ms for contact time. Gas adsorption and pore size distribution measurements For the gas adsorption studies of COF-300, the solvent exchanged sample was dried under vacuum (10-3 Torr) at room temperature overnight followed by heating at 60 C for 2 h, 80 C for 2 h, 100 C for 2 h and 120 C overnight under vacuum. The completely dried samples (0.02 g) were loaded for gas adsorption study in the sample cells. The pore distributions plots were calculated using Quenched Solid Density Functional Theory (QSDFT) and Density Functional Theory (DFT) methods using the nitrogen adsorption isotherms obtained at 77 K. S1

2 Synthesis of COFs a) RIO-1 In a high pressure vessel, 0.260g (1.24mmol) of triformylphloroglucinol and 0.300g (0.789mmol) of tetrakis- (4-aminophenyl) methane were added. The system was evacuated and had its atmosphere changed by argon. This process was repeated three times. Then, 15 ml of 1,4-dioxane and 3 ml of acetic acid (3M) were quickly added to the system. The reactor was closed instantly and gently stirred to homogenize the internal mixture. The system was then heated in a silicone oil bath, at 120 C for 72h (3 days), under magnetic stirring for obtaining RIO-1a. The same procedure, but without stirring, afforded RIO-1b. After that time, the system was slightly cooled (below the boiling point of the 1,4-dioxane, C) and the reactor was opened. The reaction medium was hot filtered with a Buchner funnel and the resulting solid washed with 20 ml of 1,3- dioxane and 20 ml of THF (tetrahydrofuran). Then the resulting yellowish-colored powder was transferred to a flask (100 ml), soaked into 50 ml THF for 72 h (3 days) to promote solvent exchange. It was filtered and dried under high vacuum for ~10h. The resulting material was transferred for a Soxhlet apparatus and treated with methanol for 72h (3 days). b) RIO-4 Figure S1. Synthesis of RIO-1 in a high pressure vessel (left); a yellow powder obtained (right). 200mg of tetrakis (4-aminophenyl)-methane (0.526mmol) and 125mg of 1,2,3-triformylphenol (0.702mmol) were transferred to a high pressure vessel. Then, 9.8 ml of 1,4-dioxane was added and the mixture was placed on ultrasound bath for about 5 min, in order to help in the dissolution of the solids, followed by the adition of 1.9 ml of acetic acid (3M) was added. The mixture was placed on ultrasound bath again for 5 min. The reactor was sealed and heated kept at 120 C for 72h (3 days). After that time, the reaction mixture was hot filtered and washed with dry 1,4-dioxane (10 ml) and dry THF (70 ml). A light orange powder was obtained and was further transferred to a Soxhlet system, using THF as solvent, where it was washed for 24h. It was then dried under high vacuum for 12 hours at a temperature of approximately 250 C. S2

3 c) COF-300 Based on the procedures of Uribe-Romo et al. (2009), tetrakis-(4-aminophenyl)methane ( g, 1.43 mmol) and terephthalaldehyde ( g, mmol) were added to a high pressure vessel. The system was evacuated and had its atmosphere changed by argon. This process was repeated three times. Then, 15 ml of 1,4-dioxane and 3 ml of acetic acid solution (3M) were added. The reactor was closed and gently stirred to homogenize the internal mixture. The system was kept at 120 C for 72 h, under magnetic stirring. After this time, the system was allowed to cool down and the reactor was opened. The reaction medium was vacuum filtered in a Buchner funnel and the resulting solid was washed with 20 ml of 1,4-dioxane and 20 ml of THF (tetrahydrofuran). Then the yellowish colored powder was transferred to a flask (100 ml), soaked into 50 ml THF for 72 h (3 days) to promote solvent exchange. After filtration it was dried under high vacuum for ~10h. d) RIO-20 Figure S2. COF-300 after filtration In a flask fitted with a reflux condenser and thermometer g (1494 mmol) of melamine and g ( mmol) of terephthalaldehyde were added, followed by the addition of 750 ml of DMSO (untreated). The system was heated with simultaneous exchange of atmosphere by argon until reflux. Initially, the reaction medium assumed orange coloration and the thermometer immersed in the reaction medium indicated a temperature around 160 C. The system was left under stirring and heating for 72h. The reaction medium was isolated and then filtered on Büchner funnel and washed with 3x25mL acetone, 3x25mL THF and 3x25mL CH 2 Cl 2. The off-white residual solid was then placed under high vacuum. Sample pretreatment The textural measurements for COFs (surface area BET, pore size, etc) were preceded by a thermal treatment under vacuum. The sample was degased and then small amounts of gas were admitted in stages into the evacuated sample chamber. The samples were subjected to vacuum and heated (1 o C/min) until 100 C, being kept at this temperature for 36 h in the vacuum line for preactivation. They were then hot transferred to the pretreatment (Quantachrome Nova 2200e) with temperature ramp and under vacuum in the equipment. Starting at 40 C, the temperature was increased at a rate of 10 C/20min until reaching 120 C and thus remained at 18h, shown below. S3

4 T (ºC) t (min) Figure S3. Pretreatment ramp for COFs. N 2 Adsorption/Desorption isotherms The pore texture characterization of the samples was performed from the physical adsorption of N 2 at 77K. The adsorption isotherms were measured volumetrically using a liquid N 2 (77K) bath to cool the sample when the gas used in the adsorption was N 2. The surface areas determined by the BET method used the adsorption or desorption data, depending on the material, in the range of P/P 0. The micropore volume was determined using the V-t method (t-plot, de Boer) on the N 2 isotherms in the region 0.2 <P / P 0 <0.5. The pore size distribution for the materials was calculated using the NLDFT method, using the set of parameters for 77K pore slits in carbonaceous adsorbent (option "N 2 at 77K on carbon, slit pore, NLDFT, equilibrium model") as implemented in the NovaWin 12000e program. Analysis The tubes with the samples were transferred while hot from the pretreatment station to the Quantachrome Nova 4200e analysis station. The isotherms were measured using a liquid nitrogen bath (77K). The gas used as adsorbate was N 2 (nitrogen) for all samples (at 77K) and additionally. N 2 and helium were used with gas regulators for free space correction and measurement. In the equipment software (NovaWin), the preselected points (P/P 0 values) to generate the adsorption/desorption isotherms of the gas in the pores were chosen, as well as values of the mass of each sample and specifications required in relation their identification. The device automatically calculates specific area information, as well as pore size and distribution. The P/P 0 relative pressure values for the BET area were chosen from 5x10-3 to 0.3 (Multi-BET). The pore size was determined using the NLDFT (Non-local Density Functional Theory) method, whose calculation model was based on carbon adsorbate (for organic) and silica (for inorganic, pore model suitable for each material. This method allows to describe the adsorption and to obtain information on the distribution of the average pore size for micro and mesoporous materials. S4

5 Thermal conductivity measurements In this study, the thermal conductivity k of the samples was measured based on the modified transient plane source technique (MTPS) through the TCi C-therm which uses a unilateral, interfacial heat reflectance sensor that applies a source of momentary constant heat in the sample. A known current is applied to the heating element of the sensor, generating a small amount of heat. The heat generated results in an increase in temperature at the interface between the sensor and the sample - typically less than 2 C. This increase in temperature at the interface induces a change in the voltage drop across the sensor element. The rate of increase of voltage in the sensor determine the thermophysical properties of the material. The equipment also allows to measure values of effusivity. For each sample, a volume of approximately 1.5 cm 3 was required to fill the compartment where the voltage sensor was (cylinder of 17 mm diameter, whose minimum sample thickness is 0.5 mm). A metal cap was placed in contact with the sample, fitting into the conductivity meter. Each reading takes about 10s and it is repeated 10 times at an average temperature of 25 C. The conductivity meter has precision better than 1% and accuracy better than 5%. The standard deviation (σ) for the 10 readings of each material was calculated, and the error was considered as three times the standard deviation (error = 3σ). This error means that the probability of a new experiment value falling in the range of the average plus or minus 3σ is 99.7%. The samples remain intact after the measurements (nondestructive method) and there is no need to prepare them. Figure S4. Measurement of thermal conductivity S5

6 Table S1. Measurements Thermal conductivity data (each sample was read 10 times, at 25 C) Sample k (W.m -1 K -1 ) COF RIO-1a RIO-1b RIO RIO Zeolite BETA ZSM S6

7 Intensity (a.u.) The powder X-ray diffraction (XRD) for COF-300, RIO-1a, RIO-1b and RIO-4 Figure S5. The powder X-ray diffraction for COF angle (2 ) Figure S6. The powder X-ray diffraction for RIO-1a shows a low crystallinity. This material was made with stirring. S7

8 Intensity (a.u.) angle (2 ) Figure S7. The powder X-ray diffraction for RIO-1b. It was synthesized without stirring. Figure S8. The powder X-ray diffraction for RIO-4 also exhibits low crystallinity. S8

9 FTIR spectra for COF-300, RIO-1ª, RIO-1b and RIO-4 Figure S9. FTIR spectra for COF-300. Figure S10. FTIR spectra for RIO-1a (RIO-1b has a similar spectrum) S9

10 Figure S11. FTIR spectra for RIO-4. NMR 13 C for COF-300, RIO-1 and RIO-4 Figure S12. CPMAS NMR 13 C COF-300 S10

11 Figure S13. CPMAS NMR 13 C RIO-1 Figure S14. CPMAS NMR 13 C RIO-4 S11

12 SEM and TEM micrographs for COF300 and RIO1a Figure S15. SEM micrograph of COF-300 S12

13 Figure S16. SEM micrograph of COF-300 S13

14 Figure S17. SEM micrograph of RIO-1a S14

15 Figure S18. SEM micrograph of RIO-1a S15

16 Figure S19. TEM micrograph of COF-300 S16