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1 Reusable Oxidation Catalysis Using Metal- Monocatecholato Species in a Robust Metal- Organic Framework Honghan Fei, JaeWook Shin, Ying Shirley Meng, Mario Adelhardt, Jörg Sutter, Karsten Meyer, and Seth M. Cohen*, Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, United States Department of Chemistry & Pharmacy, Friedrich-Alexander-University Erlangen Nürnberg (FAU) Department of NanoEngineering, University of California, San Diego, La Jolla, California 92093, United States Supporting Information * To whom correspondence should be addressed. scohen@ucsd.edu. Telephone: (858) S1

2 General Methods Starting materials and solvents were purchased and used without further purification from commercial suppliers (Sigma-Aldrich, Alfa Aesar, EMD, TCI, Cambridge Isotope Laboratories, Inc., and others). Proton nuclear magnetic resonance spectra ( 1 H NMR) were recorded on a Varian FT-NMR spectrometer (400 MHz). Chemical shifts were quoted in parts per million (ppm) referenced to the appropriate solvent peak or 0 ppm for TMS. Experimental Procedures General. Synthesis of 2,3-bis(nitrobenzyl(oxo)terephthalic acid were prepared as previously described. 1 Solvothermal Synthesis of UiO-66. ZrCl 4 (16 mg, 0.07 mmol), bdc (11.6 mg, 0.07 mmol), and acetic acid (210 mg, 3.5 mmol) were dissolved, with the aid of sonication, in 4 ml of DMF in a scintillation vial. The vial was then transferred to an isothermal oven at 120 C for 24 h. After cooling, the mixture was centrifuged, then the solid was left to soak in MeOH for 3 d, and the solution was replaced with fresh MeOH (10 ml) every 24 h. After 3 d of soaking, the solid was isolated via centrifugation at 6,000 rpm for 15 min in a fixed-angle rotor, followed by drying under vacuum. Solvothermal Synthesis of UiO-66-(OBnNO 2 ) 2. ZrCl 4 (16 mg, 0.07 mmol), bdc (5.8 mg, mmol), (OBnNO 2 ) 2 -bdc (16.3 mg, mmol), and acetic acid (210 mg, 3.5 mmol) were dissolved, with the aid of sonication, in 4 ml of DMF in a scintillation vial. The vial was then transferred to an isothermal oven at 100 C for 48 h. After cooling, the mixture was centrifuged, then the solid was left to soak in MeOH for 3 d, and S2

3 the solution was replaced with fresh MeOH (10 ml) every 24 h. After 3 d of soaking, the solid was isolated via centrifugation at 6,000 rpm for 15 min, and dried under vacuum. Synthesis of UiO-66-CAT via PSD. Ethyl acetate (EtOAc) (15 ml) was added to a vial containing ~10 mg UiO-66-(OBnNO 2 ) 2, and the vial was placed inside a Rayonet RPR-200 photoreactor with 365 nm lamps. After irradiating the samples for 2 h, the yellow supernatant was decanted. EtOAc (15 ml) was added into the vial, and the vial was placed back inside the photoreactor chamber. In a typical 24 h period, fresh EtOAc were replaced twice within a 12 h period and were agitated once in between to ensure equal exposure. After 24 h, the solid was left to soak in MeOH for 3 d, and the solution was exchanged with fresh MeOH (10 ml) every 24 h. After 3 d of soaking, the solid was isolated via centrifugation at 6,000 rpm for 15 min, and dried under vacuum. Synthesis of UiO-66-CAT via PSE. Different equivalences of catbdc were dissolved in 2 ml 4% KOH solution with sonication, followed by neutralization of the solution with a minimal amount of 1M HCl to ph = 7. Another 0.5 ml DMF was added to the mixture to obtain a clear H 2 O/DMF solution containing catbdc. UiO-66 (28 mg, 0.1 mmol, ~0.1 eq. of bdc) was introduced into the catbdc solution, followed by incubating the mixture in an isothermal oven at 85 C for 48 h. After cooling, the mixture was centrifuged, and washed thoroughly with fresh MeOH (5 10 ml). The solid was left to soak in MeOH for 3 d, and the solution was replaced with fresh MeOH (10 ml) every 24 h. After 3 d of soaking, the solid was isolated via centrifugation at 6,000 rpm for 15 min, and dried under vacuum. Internal standard studies were carried out by digestion of the entire UiO-66-CAT (via PSE) batch with diluted HF in ~1 ml d 6 -DMSO solution to which was added 24.5 mg of 2-bromoterephthalic acid (Br-bdc). The solids S3

4 were dissolved in the solution with sonication, and evaluated by 1 H NMR. Attempts at the Direct Solvothermal Synthesis of UiO-66-CAT. ZrCl 4 (16 mg, 0.07 mmol), catbdc (13.8 mg, 0.07 mmol), and a modulator (3.5 mmol; 427 mg for benzoic acid, or 210 mg for acetic acid) were dissolved, with the aid of sonication, in 4 ml of DMF in a scintillation vial. The vials were then transferred to an isothermal oven at temperatures ranging from 85 to 150 C for durations of 24 to 72 h. Mixed MOF synthesis attempts (with bdc) were carried out using the same procedure. ZrCl 4 (16 mg, 0.07 mmol), bdc (5.8 mg, mmol), catbdc (6.9 mg, mmol), a modulator (3.5 mmol; 427 mg for benzoic acid, or 210 mg for acetic acid) was dissolved, with the aid of sonication, in 4 ml of DMF in a scintillation vial. The vials were then transferred to an isothermal oven at temperatures ranging from 100 to 120 C for 24 h. After cooling, if solids appeared in the vial, the mixture was centrifuged and left to soak in MeOH for 3 d, and the solution was exchanged with fresh MeOH (10 ml) every 24 h. After 3 d of soaking, the solid was isolated via centrifugation at 6,000 rpm for 15 min, and dried under vacuum. Reaction conditions explored for the direct synthesis were given in Table S3. 1 H NMR study of PSE Supernatant. catbdc (20 mg, 0.1 mmol) were dissolved in 2 ml 4 % KOH in D 2 O solution with sonication, then the solution was titrated with a minimal amount of 1 M DCl/D 2 O solution to ph = 7. UiO-66 (28 mg, 0.1 mmol, ~0.1 equiv of bdc) was introduced into the catbdc solution, followed by incubating the mixture in an isothermal oven at 85 C for 48 h. After cooling, the mixture was centrifuged, and the top, clear layer of D 2 O was isolated for 1 H NMR. Metallation of UiO-66-CAT with Fe 3+. Fe(ClO 4 ) 3 (35 mg, 0.1 mmol Fe) or S4

5 Fe(CF 3 SO 3 ) 3 (50 mg, 0.1 mmol Fe) was dissolved in 5 ml deionized water. Then UiO- 66-CAT (31 mg, 0.1 mmol equiv bdc, prepared via PSD/photodeprotection method above) was placed into the Fe solution. The solution was sonicated to disperse the particles, followed by incubation at room temperature for 24 h. After 24 h at room temperature, the supernatant was decanted by centrifugation and the solids was washed with MeOH (4 10 ml) or until the supernatant was colorless. The solid was left to soak in MeOH for 3 d, and the solution was exchanged with fresh MeOH (10 ml) every 24 h. After 3 d of soaking, the solids were centrifuged and dried under vacuum. Metallation of UiO-66-CAT with Cr 3+. K 2 CrO 4 (20 mg, 0.1 mmol Cr) was dissolved in 2 ml deionized water. The ph of the solution was adjusted with a minimal amount of 1M HCl to 3. UiO-66-CAT (31 mg, 0.1 mmol equiv. bdc, prepared via PSE, 51% degree of catbdc functionality) was placed into the Cr 6+ solution. The solution was sonicated to disperse the particles, followed by incubation at room temperature for 1 h. After 1 h at room temperature, the supernatant was separated by centrifugation and the solid was washed profusely with deionized H 2 O (4 10 ml) and MeOH (4 10 ml), or until the supernatant was colorless. The solids were left to soak in MeOH for 3 d, and the solution was exchanged with fresh MeOH (10 ml) every 24 h. After 3 d of soaking, the solids were centrifuged and dried under vacuum. Secondary alcohol oxidation by MOF catalysts with TBHP. Secondary alcohols (1 mmol) and t-butyl hydroperoxide (TBHP, 80% t-butyl hydroperoxide in di-t-butyl peroxide/water 3:2 solution; 124 mg, 1.1 mmol or 146 mg, 1.3 mmol) were subsequently mixed and dissolved in a vial containing 1 ml chlorobenzene (or neat for solvent-free conditions). UiO-66-CrCAT (7.5 mg or 15 mg, ca or 0.01 mmol Cr) was then S5

6 transferred to the solution. The vial was incubated at 70 C for 24 h. 15 µl of the supernatant was diluted in 1 ml acetone and analyzed by GC-MS. All products (at each retention time) were isolated and analyzed by 1 H NMR and/or ESI-MS. To test recyclability, the supernatant was decanted from the catalyst and the catalyst was washed with MeOH (3 10 ml) before soaked in fresh MeOH (10 ml) for 3 d. After 3 d of soaking, the solids were centrifuged and dried under vacuum. The dried and activated MOFs were directly used for the next round oxidation catalysis for the same substrate. Secondary alcohol oxidation by MOF catalysts with H 2 O 2. Secondary alcohols (1 mmol) and H 2 O 2 (30% in H 2 O) (227 mg, 2 mmol) were mixed in a vial containing 1 ml CH 3 CN. UiO-66-CrCAT (15 mg, ca mmol Cr) was then transferred to the solution. The vial was incubated at 70 C for 24 h. 15 µl of the supernatant was diluted in 1 ml acetone and analyzed by GC-MS. Every product at every retention time was separated, and analyzed by 1 H NMR and/or ESI-MS. The supernatant was decanted from the catalyst and the catalyst was washed with MeOH (3 10 ml) before soaked in fresh MeOH (10 ml) overnight. To test recyclability, the supernatant was decanted from the catalyst and the catalyst was washed with MeOH (3 10 ml) before soaked in fresh MeOH (10 ml) for 3 d. After 3 d of soaking, the solids were centrifuged and dried under vacuum. The dried and activated MOFs were directly used for the next round oxidation catalysis for the same substrate. Powder X-ray Diffraction (PXRD) Analysis. ~20-30 mg of UiO-66 samples were dried under vacuum prior to PXRD analysis. PXRD data were collected at ambient temperature on a Bruker D8 Advance diffractometer at 40 kv, 40 ma for Cu Kα (λ= Å), with a scan speed of 1 sec/step, a step size of 0.02 in 2θ, and a 2θ range of ~5 S6

7 to 45 (sample dependent). The experimental backgrounds were corrected using Jade 5.0 software package. Digestion and Analysis by 1 H NMR. Approximately 10 mg of UiO-66 material was dried under vacuum and digested with sonication in 590 µl DMSO-d 6 (or 590 µl CD 3 OD-d 4 ) and 10 µl of 40% HF. Digestion and Analysis by ESI-MS. ESI-MS was performed using a ThermoFinnigan LCQ-DECA mass spectrometer, and the data was analyzed using the Xcalibur software suite. Samples for analysis by ESI-MS were prepared by 10 µl of digested 1 H NMR solution diluted in ~0.5-1 ml of MeOH. Thermogravimetric Analysis. ~10-15 mg of UiO-66 sample was used for TGA measurements. Samples were analyzed under a stream of N 2 with a flow rate of 10 ml/min using a TA Instrument Q600 SDT running from 50 C to 700 C with a scan rate of 5 C/min. BET Surface Area Analysis. ~50 mg of UiO-66 sample was evacuated on a vacuum line overnight at room temperature. The sample was then transferred to a preweighed sample tube and degassed at room temperature on an Micromeritics ASAP 2020 Adsorption Analyzer for a minimum of 12 h or until the outgas rate was <5 mm Hg. The sample tube was re-weighed to obtain a consistent mass for the degassed exchanged MOF. BET surface area (m 2 /g) measurements were collected at 77 K by N 2 on a Micromeritics ASAP 2020 Adsorption Analyzer using the volumetric technique. Diffuse reflectance UV-Vis Spectroscopy. ~20 mg of UiO-66 samples were dried under vacuum prior to UV-Vis analysis. Solid-state UV-Vis data were collected on a S7

8 StellarNet EPP 2000C spectrometer from 250 nm and 850 nm. The experimental backgrounds were corrected using SpectraWiz software package. Scanning Electron Microscopy-Energy Dispersed X-ray Spectroscopy. ~2-5 mg of activated UiO-66 materials was transferred to conductive carbon tape on a sample holder disk, and coated using a Cr-sputter coating for 8 sec. A Philips XL ESEM instrument was used for acquiring images using a 10 kv energy source under vacuum. Oxford EDX and Inca software are attached to determine elemental mapping of particle surfaces at a working distance at 10 mm. Around magnification images are collected. X-ray Absorption Spectroscopy (XAS). XAS measurements were obtained at the Advanced Photon Source (APS) beamline 9-BM at Argonne National Laboratory. Beamline 9-BM is equipped with a Si(111) monochromator, and focusing is achieved with a rhodium-coated toriodal mirror. XAS was measured in transmittance mode and samples were maintained at room temperature. For each sample, ~20 mg were dried under vacuum for overnight, and brushed into a thin film sealed by Kapton tape. Three scans were accumulated and averaged for each sample, and the energy was calibrated by reference to the absorption of a Fe or Cr foil measured. The data normalization and Fourier transform was done by Athena software. 2 Then the normalized data was fit using the Artemis software. 2 Extended X-ray Absorption Fine Structure (EXAFS). EXAFS fittings for UiO-66- FeCAT samples were conducted using Artemis software. 2 According to the quality of the data, 2-9 Å -1 (Fe) k-space was used for the Fourier transform and data fitting Because there is no known crystal database information file for a metal(iii)-monocatecholato S8

9 species in a MOF, a known Fe(III)-catecholato complex from the Cambridge Crystallographic Data Centre (CCDC ) was chosen as a starting model for the fitting. To accommodate the difference between the experiment and model, the fitting window was only 1-3 Å in R-space. With the four extra carbons, the R-factor was and without the four carbons the R-factor was Thus the EXAFS fittings suggest that the Fe(III)-monocatecholato species is also coordinated to methanol or methoxide rather than water or hydroxide. The speciation was assumed to be 3 methanol molecules and one methoxide to achieve charge balance. EXAFS fittings for UiO-66-FeCAT samples were conducted using Artemis software. 2 According to the quality of the data, 2-9 Å -1 (Fe) k-space was used for the Fourier transform and data fitting. A known Cr(III)-catecholato complex from the Cambridge Crystallographic Data Centre (CCDC ) was chosen as a starting model for the fitting. To accommodate the difference between the experiment and model, the fitting window was only 1-3 Å in R-space. A model with a catechol group as well as three water molecules and one hydroxide ions is set up around Cr(III) center, and the resultant R factor was given X-band EPR spectra. X-band EPR spectra were recorded on a JEOL continuous wave spectrometer JES-FA200 equipped with an X-band Gunn oscillator bridge, a cylindrical mode cavity, and a helium cryostat. Mössbauer spectra. Zero-field 57 Fe Mössbauer spectra were recorded on a WissEl Mössbauer spectrometer (MRG-500) at 77 K in constant acceleration mode. 57 Co/Rh was used as the radiation source. WinNormos for Igor Pro software has been used for the quantitative evaluation of the spectral parameters (least-squares fitting to S9

10 Lorentzian peaks). The minimum experimental line widths were 0.20 mms 1. The temperature of the samples was controlled by an MBBC-HE0106 MÖSSBAUER He/N 2 cryostat within an accuracy of ±0.3 K. Isomer shifts were determined relative to a-iron at 298 K. Table S1. BET and Langmuir surface area of UiO-66 and UiO-66-CAT. Sample BET (m 2 /g) c Langmuir (m 2 /g) c UiO ± ± 31 UiO-66 (1:1) a 1206 ± ± 15 UiO-66 (1:5) b 968 ± ± 33 a UiO-66-CAT synthesized between 1 equiv of UiO-66 and 1 equiv of catbdc. b UiO-66-CAT synthesized between 1 equiv of UiO-66 and 5 equiv of catbdc. c Based on three independent samples. Table S2. EDX results of metallated UiO-66-CAT and chromate treated UiO-66. Sample UiO-66- FeCAT % catbdc 31% Atomic Ratio of Metals a % Metalation b Zr:Fe 1:0.21(2) 68% Overall Formula Zr 6 O 4 (OH) 4 (BDC) 4.1 (catbdc) 0.6 (Fecatbdc) 1.3 Zr 6 O 4 (OH) 4 (bdc) 3 (Crcatbdc) 3 UiO-66- Zr:Cr 51% CrCAT 1:0.55(4) 108% UiO-66, Zr:Cr 0% K 2 CrO 4 1:0.04(1) N/A Zr 6 O 4 (OH) 4 (BDC) 6 a Value in parentheses is the standard deviation of the last digit b % Metalation is (no. of metalated catechol sites)/(no. of catechol sites) S10

11 Table S3. Direct Solvothermal Synthesis Attempts of UiO-66-CAT. Temp ( C) Time (h) Modulator Ligand Product 85 24~72 no catbdc None ~72 no catbdc None ~72 no catbdc None 85 24~72 Benzoic Acid catbdc None ~72 Benzoic Acid catbdc None ~72 Benzoic Acid catbdc None 85 24~72 Acetic Acid catbdc None ~72 Acetic Acid catbdc None ~72 Acetic Acid catbdc None ~72 Acetic Acid catbdc None no catbdc:bdc=1:1 Amorphous no catbdc:bdc=1:1 Amorphous Benzoic Acid catbdc:bdc=1:1 None Benzoic Acid catbdc:bdc=1:1 None Acetic Acid catbdc:bdc=1:1 Amorphous Acetic Acid catbdc:bdc=1:1 Amorphous S11

12 Figure S1. SEM of UiO-66-(OBnNO 2 ) 2 (top), UiO-66-CAT (via PSD) (middle), and UiO-66-FeCAT (bottom). S12

13 Figure S2. ESI-MS of digested UiO-66-CAT synthesized by PSD. Figure S3. Degree of catbdc functionalization of UiO-66-CAT (via PSE) with increasing equiv of catbdc used in the PSE reaction. S13

14 Figure S4. ESI-MS(-) of digested UiO-66-CAT synthesized by PSE. Figure S5. SEM of UiO-66-CAT (via PSE) with 75% catbdc incorporation. S14

15 Figure S6. 1 H NMR of the PSE supernatant between UiO-66 and catbdc in D 2 O solution (details in Experimental Section). Figure S7. EDX of UiO-66-FeCAT, showing atomic ratio of 1:0.21 (Zr:Fe). S15

16 Figure S8. PXRD of UiO-66-CrCAT (top) and UiO-66-FeCAT (bottom). Figure S9. Diffuse reflectance UV-Vis spectrum of Fe(ClO4)3, UiO-66-CAT, and UiO66-FeCAT. S16

17 Figure S10. EPR absorption spectrum (bottom) for better illustration of the minute radical impurity. Figure S11. EPR spectra of sample UiO-66 in solid state at 9, 66, and 289 K. Modulation width 2 mt, time constant 0.1 s; at 9 K: frequency GHz, power 0.3 mw; at 66 K: frequency GHz, power 1 mt; at 289 K: GHz, power 1 mt. S17

18 Figure S12. EDX of UiO-66-CrCAT, showing atomic ratio of 1:0.55 (Zr:Cr). Figure S13. SEM of UiO-66-CrCAT. Figure S14. EDX of UiO-66 treated with K 2 CrO 4 under ph=3, showing the atomic ratio of 1:0.04:0.07 (Zr:Cr:K). S18

19 Figure S15. XPS of UiO-66-CrCAT (top), Cr(NO 3 ) 3 (middle) and K 2 CrO 4 (bottom). Figure S16. XANES of UiO-66-CrCAT (black), K 2 CrO 4 (red) and Cr(acac) 3 (blue). S19

20 Figure S17. 1 H NMR of digested UiO-66-CAT (via PSE) after incubation in 2-heptanol (black), cyclooctanol (red), 1-phenylethanol (blue) and 5α-cholestan-3ß-ol (magenta) at 70 C for 24 h. The ratio of substrate to total ligand content in the MOFs is 0.79:1 for 2- heptanol, 0.43:1 for cyclooctanol, and 0.12:1 for 1-phenylethanol. The digestion was carried out with diluted HF in CD 3 OD for MOFs absorbed with 2-heptanol, 1- phenylethanol and 5α-cholestan-3ß-ol and with diluted HF in d 6 -DMSO for cyclooctanol included MOFs. S20

21 Figure S18. Yields of 2-heptanol oxidation with TBHP and UiO-66-CrCAT as catalysts under solvent-free condition (black) or 1 ml chlorobenzene (red). After 2 h, UiO-66CrCAT was removed, showing no leaching of catalytically active species into the solution. Yields were determined by GC-MS. Figure S19. PXRD of UiO-66-CAT (via PSE) and UiO-66-CrCAT after incubation in aqueous solution for 24 h showing the chemical robustness of these MOFs. S21

22 Figure S20. TGA of UiO-66-CAT (via PSE) and UiO-66-CrCAT under N2. Figure S21. PXRD (left) and SEM (right) of UiO-66-CrCAT after catalysis. S22

23 Figure S22. XANES (left) and EXAFS (right) of UiO-66-CrCAT before catalysis (black) and after catalysis (red). Figure S23. XPS of UiO-66-CrCAT after catalysis. S23

24 Transform Magnitude R (Å) Figure S24. Fourier transformed EXAFS spectrum of UiO-66-FeCAT prepared from Fe(CF 3 SO 3 ) 3. Black solid line is experimental data, red dashed line is best fit to data, and blue dotted line is fitting window. Figure S25. EXAFS spectrum of UiO-66-CrCAT. Black solid line is experimental data, red dashed line is best fit to data, and blue dotted line is fitting window. S24

25 References (1) Tanabe, K. K.; Allen, C. A.; Cohen, S. M. Angew. Chem., Int. Ed. 2010, 49, (2) Ravel, B.; Newville, M. Journal of synchrotron radiation 2005, 12, 537. S25