One step facile synthesis of amine-functionalized COF-1 with enhanced hydro-stability

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1 One step facile synthesis of amine-functionalized COF-1 with enhanced hydro-stability Yi Du *, David Calabro, Bradley Wooler, Pavel Kortunov, Quanchang Li, Stephen Cundy, and Kanmi Mao * Corporate Strategic Research, ExxonMobil Research and Engineering, 1545 US22, Annandale, NJ Synthesis APTES-COF-1: In a dry N 2 environment, 0.25 g 1,4-benzenediboronic acid (BDBA) was mixed with g (3-aminopropyl)triethoxysilane (APTES) in 10 ml of a 1:1 v/v solution of mesitylene:1,4- dioxane. The reaction mixture was sealed with dry N 2 and sonicated for 60 minutes. The reaction vessel was evacuated, then the solution was heated to 75 C for 20 hours. A white powder was obtained after filtration in atmospheric conditions, and was subsequently dried under vacuum at 120 C. Products were stored in room conditions. TEOS COF-1: In a dry N 2 environment, 0.25 g 1,4-benzenediboronic acid (BDBA) was mixed with g tetraethyl orthosilicate (TEOS) in 10 ml of a 1:1 v/v solution of mesitylene:1,4-dioxane. The reaction mixture was sealed with dry N 2 and sonicated for 60 minutes. The reaction vessel was evacuated, then the solution was heated to 75 C for 20 hours. A white powder was obtained after filtration in atmospheric conditions, and was subsequently dried under vacuum at 120 C. Products were stored in room conditions. Propylamine COF-1: In a dry N 2 environment, 0.25 g 1,4-benzenediboronic acid (BDBA) was mixed with g propylamine in 10 ml of a 1:1 v/v solution of mesitylene:1,4-dioxane. The reaction mixture was sealed with dry N 2 and sonicated for 60 minutes. The reaction vessel was evacuated, then the solution was heated to 75 C for 20 hours. A white powder was obtained after filtration in atmospheric conditions, and was subsequently dried under vacuum at 120 C. Products were stored in room conditions. TEOS-Propylamine COF-1: In a dry N 2 environment, 0.25 g 1,4-benzenediboronic acid (BDBA) was mixed with g tetraethyl orthosilicate (TEOS) and g propylamine in 10 ml of a 1:1 v/v solution of mesitylene:1,4-dioxane. The reaction mixture was sealed with dry N 2 and sonicated for 60 minutes. The reaction vessel was evacuated, then the solution was heated to 75 C for 20 hours. A white powder was obtained after filtration in atmospheric conditions, and was subsequently dried under vacuum at 120 C. Products were stored in room conditions.

2 COF-1-APTES: In a dry N 2 protection environment, 0.25 g benzenediboronic acid (BDBA) was mixed in 10 ml of a 1:1 v:v solution of mesitylene: 1, 4 - dioxane. The reaction mixture is sealed with dry N 2 and sonicated for 30 minutes then heated to 120 C for 3 days to afford white powder of pure staggered COF-1 phase. Upon complete synthesis, g (3-Aminopropyl)triethoxysilane (APTES) is added to the COF-1 dispersion in the synthesis solvent, and heat to 75 C overnight to afford white powder of pure staggered COF-1-APTES phase. The product was filtered and washed with acetone in normal lab environment and air dry. Products were stored in room conditions. Oriented COF-1 on glass slides grafted by APTES: In a dry N 2 protection environment, g (3- Aminopropyl)triethoxysilane (APTES) was mixed in 10 ml toluene at the presence of glass slides or glass tubes, reflux at 120 C overnight, filter, and obtained APTES-grafted-glass g benzenediboronic acid (BDBA), the APTES-grafted-glass are then placed in 10 ml of a 1:1 v:v solution of mesitylene: 1, 4 - dioxane. The reaction mixture is sealed with dry N 2 and sonicated for 30 minutes then heated to 120 C for 3 day to afford white powder of pure staggered COF-1 phase. The product was filtered and washed under N 2 protection, dried and characterized immediately. Stability Tests The products were tested for atmospheric stability with X-ray diffraction (XRD). After synthesis, each sample was scanned with XRD, then kept in the same sample holder to maintain the same background for all subsequent scans. The samples were stored in atmospheric conditions (20-25% r.h.) and scanned intermittently over a period of two weeks to track their stability in air. The samples that proved stable over this period (APTES COF-1 and TEOS-Propylamine COF-1) were then subjected to higher humidity conditions. To simulate a more humid environment, air was bubbled through water and flowed into a chamber containing the samples. After 20 hours in this environment, during which the humidity ranged from 50-58% r.h., samples were checked by XRD for decomposition. 1 Reference 1. Du, Y.; Mao, K.; Kamakoti, P.; Wooler, B.; Cundy, S.; Li, Q.; Ravikovitch, P.I.; Calabro, D. J. Mater. Chem. A 2013,1, Environmental X-ray Diffraction (EXRD) Time-resolved, in situ EXRD data were typically measured on 50 mg of staggered APTES-COF-1 phase and heated to 200 to 230 C, respectively, which is in average 40 C higher than the equivalent COF-1 case. 2 EXRD patterns were recorded on a PANalytical X Pert Pro instrument in reflection mode with Cu Kα radiation (λ = Å). The accelerating voltage was set at 45 kv with 40 ma current. The diffractometer was equipped with X Celerator detector and Anton Paar HTK-16 high temperature chamber equipped with Pt heating strip. Scan rates were typically 0.21 s-1 (continuous scan, step size , 2

3 time per step 10 s). 2θ is ranged from 5.5 to Antiscatter slit, receiving slit, and divergent slit were all fixed at 1/4. 1,2 The value of the extent of reaction is defined by α(t) = I hkl (t)/i hkl (max), where I hkl (t) represents the integrated intensity of the hkl reflection at time t and I hkl (max) is the maximum intensity of that reflection. A plot of extent of reaction (α = I(t)/Imax) as a function of time is shown in Figure S5, S6 and S7. The data suggest a one-step phase-conversion process as the α(t) curves of staggered COF-1 and eclipsed COF- 1 cross close to α = 0.5. At each temperature, the experimental data were fitted to the Avrami Erofe ev model ([ ln(1 α)]1/n = k(t t ind )) in order to calculate the reaction exponent, n, and the reaction rate, k. 3 A Sharp Hancock plot was generated in Figure S5, S6 and S7 to evaluate the linear dependence of ln[ ln(1 α)] vs ln(t). All kinetic data are summarized in Table S1. The reaction rate increases as temperature increases, and the value of Avrami exponent n is found to increase from 0.53 to 0.65, correspondingly. Using time-resolved, in situ environmental X-ray diffraction (EXRD) modeled with the Avrami- Erofe ev model, we are able to extract the activation energy for this phase change to be 122.1(7) kj/mol, which is 51 kj/mol higher than the activation energy of normal, APTES-free COF-1 s phase change. This is an effective activation energy which includes the activation energy for the phase conversion due to the in plane shear movement in addition to the diffusion and evaporation energy required for removing the trapped mesitylene solvent. This similar phase transition further confirms the structural similarity between APTES-COF-1 and COF-1. Reference: 2. Du, Y.; Calabro, D.; Wooler, B.; Li, Q.; Cundy, S.; Kamakoti, P.; Colmyer, D.; Mao, K.; Ravikovitch, P., J. Phys. Chem. C 2014, 118, Du, Y.; O Hare, D. Inorg.Chem. 2008, 47, Solid-state nuclear magnetic resonance (SSNMR) 1 H and 11 B SSNMR measurements were performed at MHz for 1 H and MHz for 11 B, using a Varian 500 MHz InfinityPlus spectrometer (11.7 T) equipped with a 1.6-mm FastMAS TM triple resonance probe at magic angle spinning (MAS) 40 khz. 29 Si spectrum was measured at 79.3 MHz using a Varian 400 MHz InfinityPlus spectrometer (11.7 T) with a 7.5 mm double resonance probe at MAS rate of 5 khz. All experiments were implemented at room temperature. 1 H and 29 Si chemical shifts are referenced to tetramethylsilane as zero ppm. 11 B chemical shifts are referenced to BF 3 O(C 2 H 5 ) 2 as zero ppm. 11 B MAS spectrum was acquired using π/12 excitation pulse with 2 s recycle delay. The 11 B two dimensional (2D) Multiple quantum (MQ) MAS NMR experiments were recorded using z-filter method 4 with a typical t 1 increment of 8µs in F1 dimension. For 2D 1 H- 1 H double quantum (DQ) MAS, a rotor-synchronized back-to-back (BABA) sequence 5 was used, DQ excitation/reconversion length was 50 µs, 100 rows with 25 µs t 1 increment with 100 rows were used. 29 Si cross polarization (CP) MAS was recorded using contact time of 3 ms and recycle delay of 2 s. 3

4 References: 4. Amoureux, J. P.; Fernandes, C.; Steuernagel, S J. Magn. Reson., Ser. A 1996, 123, Feike, M.; Demco, D. E.; Graf, R.; Gottwald, J.; Hafner, S.; Spiess, H. W. J. Magn. Reson. A 1996, 122, 214. Thermogravimetric analysis (TGA) measurement. Thermogravimetric analysis (TGA) was carried out on a TA Instruments Q5000IR V3.5 Build 253 machine. The sample (ca. 4 mg) was mounted in a 100 µl platinum pan and heated at a rate of 5 C min -1 between room temperature and 800 C under a flow of air. Autosorb CO 2 isotherms and Brunauer, Emmett and Teller (BET) measurements APTES-COF-1 or COF-1-APTES sample was degassed to get rid of any contaminants adsorbed on the surface by evacuating it to 10-5 torr dynamic vacuum and simultaneously heating to 220 C for 4 hours in Autosorb-1-C Analyzer of Quantachrome Instruments. A 77 K nitrogen isotherm was then performed on this sample from 0 to 1 atm (1 atm = P 0 ). The Brunauer, Emmett and Teller (BET) model was applied to 5 points of the isotherm for P/P o between 0.01 to 0.1. A 30 o C, 50 o C, and 80 o C CO 2 isotherms are also performed on this sample from 0 to 1 atm (1 atm = P 0 ). High pressure gas sorption Method. The study of gas adsorption on APTES-COF-1 was performed using commercial volumetric gas adsorption analyzer HIDEN IMI manufactured by HIDEN Isochema Ltd. The amount of gas adsorbed in the sample is determined by the change of gas pressure in a known volume at fixed temperature (Scheme 1). Scheme 1. Schematic of volumetric gas adsorption analyzer. The system includes the thermostated dosing chamber with DRUCK pressure transducer, gas supplies, vacuum pump and separately thermostated samples chamber connected through pneumatically actuated diaphragm valve with low internal volume. 4

5 The method relies on precise determination of dosing chamber volume V 1 and sample chamber volume V 2 (with and without the actual sample), which is performed with helium before each experiment, very accurate control of temperature T 1 and T 2 of both dosing and sample chambers and accurate measurements of the gas pressure during the experiment. Experimental procedure includes deep outgassing of the entire system to reach 1x10-8 mbar to evacuate molecules from both chambers and from the sample, isolation of dosing and sample chambers, pressurization of the dosing chamber with the gas of interest at pressure P 1 and opening the isolation valve to let gas fill the sample chamber, adsorb in the sample at pressure P 2. Given the amount of gas initially injected in the dosing chamber kept at temperature T 1 and pressure P 1 is calculated by the real gas law: = the amount of gas adsorbed in the sample thermostated at temperature T 2 is then calculated as:. = where V 2 is a volume of the sample chamber minus the volume of the sample itself, R is a gas constant and Z is compressibility factor of the given gas at given temperature and pressure. We used NIST fluid property database to determine the compressibility values for all gases under study. It has to be noted that such volumetric method provides the amount of gas in the sample, which cannot be explained by the real gas law and interpreted as adsorbed gas or excess adsorption. To calculate the absolute amount of gas in the pores of the sample, the following equation is used:. =. + where is a gas density at P 2 and T 2 and V p is volume of pores of the sample determines as cc/g for the studied APTES-COF-1 by BET method described above. Experimental. Adsorption properties of APTES-COF-1 was studied with methane and carbon dioxide up to 63 bar and 37 bar, respectively, to examine the possible changes of adsorption capacity relative to the parent material COF-1 sample without stabilizing APTES groups. Figure S15 shows the values of absolute adsorption of CH 4 and CO 2 measured over the broad range of pressures at 30 0 C. Carbon dioxide adsorbs stronger on the pore surface of APTES-COF-1 reaching 3.9 mmol/g at 35 bar while absolute uptake of methane is 2.3 mmol/g at 35 bar and 2.8 mmol/g at 60 bar. Adsorption and desorption branches of the CO 2 isotherm match and CO 2 chemisorption on coordinated propylamine group is not detected. The overall CO 2 uptake in APTES-COF-1 is comparable with that in the parent material COF-1 6, 7, and we conclude that APTES groups do not reduce the sorption capacity of APTES- COF-1 while making the material more stable. Reference 6. Côte, A.; Benin, A.; Ockwig, N.; O Keeffe, M.;Matzger, A.; Yaghi, O., Science 2005, 310, Yaghi, O.; Furukawa, H., J. Am. Chem. Soc., 2009, 131,

6 Figure S1. XRD patterns of APTES COF-1 made at 75 C for one day and the product without APTES made at 75 C for one day. The # symbol indicates peaks due to the benzene diboronic acid starting materials. 6

7 Figure S2. XRD patterns of APTES COF-1 made at 75 C after exposed to 90% r.h. for one hour and 20 hrs. 7

8 200 C 215 C 230 C AA phase AB phase Figure S3. In situ XRD 3 D plot to record the phase conversion from AB staggered APTES-COF-1 to AA eclipsed APTES-COF-1 at 200, 215 and 230 C, respectively. 8

9 a b Figure S4. (a) Plot of α (t) for 110 of staggered APTES-COF-1 and 100 of eclipsed APTES-COF-1 at 200 C; (b) Sharp-Hancock plot to obtain reaction rate k (exp(intercept/slope)) and reaction order n (the Slope of the fitting). 9

10 a b Figure S5. (a) Plot of α (t) for 110 of staggered APTES-COF-1 and 100 of eclipsed APTES-COF-1 at 215 C; (b) Sharp-Hancock plot to obtain reaction rate k (exp(intercept/slope)) and reaction order n (the Slope of the fitting). 10

11 a b Figure S6. (a) Plot of α (t) for 110 of staggered APTES-COF-1 and 100 of eclipsed APTES-COF-1 at 230 C; (b) Sharp-Hancock plot to obtain reaction rate k (exp(intercept/slope)) and reaction order n (the Slope of the fitting). 11

12 Table 1. Kinetic data summary for phase conversion from AB staggered APTES-COF-1 to AA eclipsed APTES-COF-1 T/ C n a k a / 10-3 s -1 t 0.5 b /s ± ± ± ± ± ± a Least squares fit to the Avrami-Erofe ev model: α = 1 exp{-[k(t-t ind )] n ]}. b t 0.5 is defined as the time when α(t) = 0.5 Figure S7. Arrhenius plot to determine the activation energy for phase conversion from Staggered APTES-COF-1 to Eclipsed APTES-COF-1 12

13 Table 2. Elementary analysis for APTES-COF-1. The proposed formula is (NC 3 H 8 SiO 1.5 ) 1 (C 3 H 2 BO) 6 (C 9 H 12 ) 0.7 (APTES-COF-1) APTES-COF-1 (wt%) B C H N GLI Procedure ME-70 (25.93 mg) GLI Procedure ME-12-a (1.588 mg) GLI Procedure ME-12-a (1.384 mg) Figure S8. 11 B MAS NMR of APTES-COF-1. Figure S9. 29 Si CPMAS NMR of APTES-COF-1. 13

14 Figure S10. 2D 11 B MQMAS NMR of APTES COF-1 after 200 C in vacuum. Figure S11. 2D 1 H- 1 H DQMAS spectra of as-synthesized APTES-COF-1(left) and as-synthesized COF-1 (right). Both samples contain mesitylene. The top-middle 1D spectrum is the slide spectrum (marked as a dash line) of 14

15 2D spectrum of APTES-COF-1(left); the bottom-middle 1D spectrum is the slide spectrum (marked as a dash line) at the same position of COF-1 2D spectrum (right). H APTES refers to proton from APTES, H m refers to methyl proton of mesitylene, H ar is aromatic proton of mesitylene, H COF is proton from COF-1. Intermolecular connectivities, H COF -H APTES, H COF -H m, and H COF -H APTES were well identified. Figure S12. TGA of COF-1 and APTES-COF-1. *ref. COF-1 data is from ref 1. 15

16 Figure S13. CO 2 isotherms for APTES-COF-1 at 20 C with different pretreat conditions. *ref. activated COF-1 data is from ref 1. Figure S14. CO 2 isotherms at 30 C, 50 C and 80 C for APTES-COF-1, pretreated at 220 C under vacuum for four hours. 16

17 (a) 17

18 (b) Figure S15. High pressure (a) CO 2 and (b) CH 4 isotherms at 30 C for APTES-COF-1, pretreated at 220 C under vacuum for four hours. (black) excess uptake; (red) absolute uptake; (solid) adsorption; (empty) desorption. The green cross is the reported uptake for COF-1 correspondingly. 7 18

19 Figure S16. 2D 1 H- 1 H DQMAS spectrum of APTES-COF-1 after 200 C vacuum. Notations are the same as Figure S11. Intermolecular connectivity, H COF -H APTES was well identified. Figure S17. Scheme of formation of APTES-COF-1. 19

20 Figures S18, XRD patterns of COF-1-APTES in the as synthesis gel. The isolated white product is called COF-1-APTES. Stability test for the as prepared sample at day 1, day 8, and day 22 to prove no degradation has been observed. 20

21 Figure S19. 2D 11 B MQMAS NMR of COF-1 + APTES. APTES is added after the complete synthesis of COF-1 21

22 Figures S20, XRD patterns of TEOS-COF-1 made at 75 C for 1 days by adding TEOS in the original starting materials. # represent phase from benzene diboronic acid, the starting material, indicating the reaction is not complete. Figures S21, XRD patterns of propylamine-cof-1 in the original starting materials. # represent phase from benzene diboronic acid, the starting material, indicating the product is not stable, decomposes and forms the starting materials again. Stability test for the as prepared sample at day 1, day 5, and day

23 Figure S22. 2D 11B MQMAS NMR of Propylamin-COF-1. 2/3 of B is B [3], and the remaining 1/3 is B [4]. 1 23

24 Figures S23, XRD patterns of COF-1 made at 75 C for 1 day by adding propylamine and TEOS simultaneously in the original starting materials. # represent phase from benzene diboronic acid, the starting material, indicating the product is not stable, decomposes and forms the starting materials again. Stability test for the as prepared sample at day 1, day 3, and day 10. From day 10, the sample is exposed to 90% r.h. for one day, and it is decomposed. 24

25 Figure S24. Scheme of formation of COF-1 on APTES grafted glass slides. The powder pattern used COF-1 staggered AB model and is simulated for comparison. All observed diffractions can be indexed to P6/3mmc symmetry. The index and unit cell parameter are also made in to the Table below for reference. 25

26 APTES-COF-1 Hexagonal, P6/3 mmc, a=b= , c= Å hkl 2θ(cal) 2θ(obs) 2θ d(cal) d(obs) d Int% Figure S25. XRD pattern of APTES-COF1 and its diffraction indexing table. We ve also performed some structure simulation to locate the APTES molecules using the Reflex Powder Refinement in Materials Studio 6.0. Due to the limited and broad diffraction peaks, we have not refined the each atom positions and thermal factors. Instead, we have a simple structure model by setting mesitylene and APTES as independent motion groups to refine freely. At converging, the Rwp is 4.79% and Rp is 3.55%, and the simulated pattern matches the experimental pattern well. The simulated and experimental pattern are listed below, together with view perpendicular to 002, and 100, respectively. Both APTES and mesitlyene preferred to sit right inside the 15A pore window in COF-1 structure. They offset by ½ unit cell due to the AB staggered configuration. From the our proposed chemical formula, the molar ratio of APTES and mesitylene should be 1:1, and the molar ratio of APTES to the B center should be 1:3. The distance between the APTES to COF1 framework is less than 5A. We believe mesitylene and APTES are distributed randomly inside COF-1 structure. This can also be supported by the NMR and the high activation energy of in situ XRD as shown in SI. 26

27 Figure S26. Simulated and experimental XRD pattern of APTES-COF1 and its structure model corresponding. 27