Supporting Information for the article Electroactive Ferrocene At or Near the Surface of

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1 Supporting Information for the article Electroactive Ferrocene At or Near the Surface of Metal Organic Framework UiO-66 Rebecca H. Palmer, Jian Liu, Chung-Wei Kung, Idan Hod, Omar K. Farha,,, and Joseph T. Hupp*, Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States Department of Chemistry, Ben-Gurion University of the Negev, Beer-Sheva, , Israel Department of Chemical and Biological Engineering, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, United States Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia Contents: Figure S1. HNMR of 1-propenoic-ferrocene Figure S2. XPS of UiO-66-Fc-db-COO... 3 Figure S3. Powder X-ray diffraction patterns of samples Figure S4. Nitrogen isotherms of UiO-66 with and without ferrocene derivatives installed... 5 Figure S5. Cross section of UiO-66-Fc-db-COO film after electrochemistry in 0.1 M KCl (aq). 6 Figure S6. Cyclic voltammetry of ferrocene derivatives Figure S7. Cyclic voltammetry of UiO-66-Fc-db-COO... 8 Figure S8. SEM image of UiO-66-Fc-db-COO Figure S9. Cyclic Voltammetry of UiO-66-Fc-db-COO films in different electrolytes in acetonitrile Figure S10. Peak current dependence on scan rate Figure S11. CVs of UiO-66 films with and without ferrocene derivatives Table S1. Ferrocene loading near surface measured by XPS... 3 Table S2. BET Areas... 6 S-1

2 Figure S1. HNMR of 1-propenoic-ferrocene. S-2

3 Figure S2. XPS of UiO-66-Fc-db-COO In the left column, the Zr3d scan are shown, with Fe2p scan in the right column. The top XPS scans are UiO-66-Fc-db-COO without ion beam etching. The bottom scans were taken after 10 seconds of ion (Ar + ) beam etching. The spectra were fitted, and ratios are listed below in Table S1. Table S1. Ferrocene loading near surface measured by XPS Ion Beam Etching (seconds) Ferrocene per Node S-3

4 Figure S3. Powder X-ray diffraction patterns of samples. Powder X-ray diffraction patterns of (top to bottom) UiO-66-Fc-COO after CV, UiO-66-Fc- COO, UiO-66-Fc-db-COO after CV, UiO-66-Fc-db-COO, UiO-66, and a simulated pattern for UiO-66. CVs were measured in 0.1 M KCl (aq) at a 10 mv/s scan speed. S-4

5 Figure S4. Nitrogen isotherms of UiO-66 with and without ferrocene derivatives installed UiO-66 with a BET area of 1620 m 2 /g (top), UiO-66-Fc-COO with BET area of 1070 m 2 /g (center), and UiO-66-Fc-db-COO with a BET area of 910 m 2 /g (bottom). Closed points are from the adsorption measurement while open points are from the desorption measurement. S-5

6 Table S2. BET Areas from isotherm measurement (Figure S3) Sample BET area (m 2 /g) UiO UiO-66-Fc-COO 1070 UiO-66-Fc-db-COO 910 Figure S5. Cross section of UiO-66-Fc-db-COO film after electrochemistry in 0.1 M KCl (aq). S-6

7 Figure S6. Cyclic voltammetry of ferrocene derivatives. 10 mm ferrocenecarboxylic acid (grey), 10 mm 1-propenic acid ferrocene (black) and 0.1 M TBAPF 6 (black dash) in acetonitrile. All curves were measured at 25 mv/s scan speed with a glassy carbon working electrode. Both ferrocene derivatives have 0.1 M TBAPF 6 as a supporting electrolyte. S-7

8 Figure S7. Cyclic voltammetry of UiO-66-Fc-db-COO 0.1 M KCl (aq) at 10 mv/s scan speed, N 2 purged (green UiO-66-Fc films, blue FTO; dashed line measured in solution 1, solid line measured in solution 2). Expanded y-axis showing FTO scanned in same 0.1 M KCl (aq) solutions in which UiO-66-Fc-db-COO was scanned. Figure S8. SEM image of UiO-66-Fc-db-COO. S-8

9 The round particles were taken as spheres for simplicity and an estimate of nodes on the surface was compared to nodes in the particle using the dimensions of UiO-66 from the crystallographic information file. 1 Approximately 2% of nodes are on the surface of a 0.16 m UiO-66 particle. The percent of nodes located at the exterior surface of the MOF was estimated by approximating the crystallites as spheres of diameter 160 nm (the measured average size). Given the length of linkers, we considered nodes residing within the outermost 1 nm of a crystallite to be sited at the external surface. The percentage present at the surface can then be estimated as 100% x [1 - (159 nm/160 nm)exp(3)), or ~2%. Additionally, we calculated the depth of accessible ferrocene, at the maximum percent of addressable ferrocene (22%). Assuming the average particle size of UiO-66, (diameter 160 nm) has a uniform distribution of ferrocene, we have a total volume, V tot. Inside the particle, there is a spherical volume, V inner, where no ferrocene is addressable. Near the exterior, there is a shell with volume, V shell, where the accessible ferrocene resides. The thickness of V shell can be calculated through R tot r inner = X shell where R tot is the radius of the total sphere, r inner, is the radius of the inner sphere (where no ferrocene is addressable), and X shell is the thickness of the spherical shell. The radius of r inner can be calculated by solving V inner = V tot *0.78 = 4/3 * *r inner 3 (note: 0.78 is the non-addressable ferrocene located in V inner ). Next, we attempt to account for the higher loading we find by XPS on the exterior of the UiO-66 particles. First, the volume of a shell can be represented by V shell = 4/3 pi*[r tot 3 (R tot X shell ) 3 ].The total ferrocene in this volume is 4/3 pi*[r tot 3 (R tot X shell ) 3 ]* (nodes/volume) *(Fc/node). We can compare the total ferrocene or a shell with thickness of 6 nm and loading of 1.3 Fc/node that has the same amount of ferrocene as a shell with thickness X shell2 and loading of 4.5 Fc/node.We find: 4/3 pi*[r tot 3 (R tot 6) 3 ]*(nodes/volume)*(1.3 Fc/node) = 4/3 pi*[r tot 3 (R tot X shell2 ) 3 ]*(nodes/volume)*(4.5 Fc/node) Here, R tot = 160 nm. Solving for X shell2 = 1.6 nm or ~2 nm S-9

10 Figure S9. Cyclic Voltammetry of UiO-66-Fc-db-COO films in different electrolytes in acetonitrile. From top to bottom, the electrolytes are 0.1 M tetrabutylammonium tetraphenyl borate (blue), 0.1 M tetrabutylammonium hexafluorophosphate (yellow), and 0.1 M lithium perchlorate (green). Scan speed was 50 mv/s. S-10

11 Figure S10. Peak current dependence on scan rate a) Cyclic voltammetry of UiO-66-Fc-db-COO using scan rates from 5 mv/s to 200 mv/s. Scans were obtained in nitrogen purged 0.1 M KCl. b) Peak currents for both oxidation (grey) and reduction (blue), taken from a), plotted against (scan rate) 1/2 with trendlines. S-11

12 UiO-66-Fc-COO: UiO-66-Fc-COO showed a loading of ferrocene per Zr 6 node and a BET area of 1070 m 2 /g. Redox peaks were observed for UiO-66-Fc-COO (centered around 0.38 V). Figure S11. CVs of UiO-66 films with and without ferrocene derivatives. Curves are UiO-66-Fc-COO (navy, solid), UiO-66-Fc-db-COO (blue, dash), UiO-66-Fc-db-COO (light blue, solid), and FTO (grey dash). CVs were taken in 0.1 M KCl (aq) bubbled with N 2 at a 10 mv/s scan speed. References 1. Cavka, J. H.; Jakobsen, S. r.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.; Lillerud, K. P., A New Zirconium Inorganic Building Brick Forming Metal Organic Frameworks with Exceptional Stability. J. Am. Chem. Soc. 2008, 130 (42), S-12