1. Nanoporosity – where is it useful in chemistry? David Avnir Institute of Chemistry The Hebrew University of Jerusalem Nano Center Meeting, Ashkelon, March 29-30, 2015

2. 1. The material at focus - silica

3. Silica

4. Controlled nanoporosity Surface area and pore volume of silica as a function of pH and water/silane ratio in the sol- gel process

5. Functionality within a sol-gel matrix Monoliths Powders Particles This-films

7. 2. Chemical sponges – diffusion considerations

8. Sol-Gel Sponges Hagit Frenkel-Mullerad

9. The reaction kinetics can be followed in two ways: 1.Following the visible absorption of bromine 2. Following the decrease in pH

10. Kinetics of the reaction through follow-up of Br 2 consumption Vinylated silica

11. Kinetics of the reaction as detected by HBr release 2.2 2.25 2.3 2.35 2.4 01020304050 pH Time (min) Kinetics of reactivity in nanopores depends on the analytical probe! X 10 slower

12. Time (s) 0.5 0.6 0.7 0.8 0.9 1 1.1 024681012 VTS ATS BTS OTS A/Ao Time (s) Kinetics depends also on the fine details of the hybrid material, even if the functionality is the same: Vinyl, allyl, butyl, octyl. The shorter chains are much more reactive than the longer ones - why? Initial rates

13. A schematic view of the possible micellar nano-phase zones Reactivity depends on the specific nano structure of the hybrid material

14. 3. Photochemistry

15. Electron transfer Py Light Py* - the donor Py* + MV 2+ - the acceptor MV.+ + Py + 2MV.+ + 2H 3 O + 2MV 2+ + H 2 + 2H 2 O The classical problem: MV.+ + Py + MV 2+ + Py Example 1: Solar energy storage - solving the problem of back-reaction Energy storing pair Useful reaction back-reaction

16. Py*@silica + TV 2+ Four hours, 5% yield of separated pair The nanoporosity approach: I. Separate spatially the donor and the acceptor by entrapment in a sol-gel matrix II. Allow them to communicate through the nanopores with a shuttler A. Slama-Schwok, M. Ottolenghi TV + + Py + @silica MV 2+ @silica + TV + TV +2 + MV + @silica TV + + Py + @silicaPy@silica + TV 2+ TV 2+ Py MV 2+ The redox potential of the MV pair is smaller than that of the TV pair

17. D. Levy Example 2: Affecting the direction of photochromism by tailoring the surface of the nanopores Isomerization of spiropyrans

18. Colorless Colored Controlling the directionality of photochromism Reversed photochromism in silica sol-gel matrices

19. …but normal photochromism in ethylated silica Colorless Colored

20. 3. Sensors: Extraction of a library of reactivities from a single molecule

21. Getting a library of acid/base sensors from a single molecule nanopore effects Anionic AF Zwitterionic ET(30) + Claudio Rottman

22. Affecting the immediate environment by co-entrapment of surfactants within the nanocages

23. E T (30), an acid or a base – your choice: The interpretation

24. Continuous range of acids/bases by using a surfactant mixture at varying proportions E T (30)

25. Huge pK i shift for AF: 8 orders of magnitude

26. 4. Catalysis

27. Cl 3 OCH 2 CO 2 H Cl 3 24 h (75%) Cl (99%) C CCl 3 1st example: Superior synergistic catalyst for green chemistry Two components in a nano-cage: Catalytic synergism Hydrogenation of chlorinated environmental pollutants Cl C H CH 3 (90%) OH H Cl 6 h H 2 O ClCH 2 CH 2 Cl (44%)+ (26%) = OH O O O hexane O O 24 h ClCH 2 CH 2 Cl Cl (93%) 24 h R. Abu-Reziq, J. Blum The combined catalyst: Pd nanoparticles + [Rh(cod)Cl] 2 Chlorophenols 2,4,5-T PCBs DDT Cl-dioxins

28. C. Bianchini, R. Psaro et al, J. Am. Chem. Soc. Mechanism suggested by Bianchini, Psaro et al: The confinement of the two catalysts within a cage

29. 2nd example: One-pot multistep catalytic processes with opposing reagents F. Gelman, J. Blum Cutting the need for separation steps

30. F. Gelamn, J. Blum Three steps oxidation/reductions in one pot RhCl[P(C 6 H 5 ) 3 ] 3 91%

31. 5. Imprinted nanoporosity

32. 4th example: Tailored nanoporosity by imprinting Directing the seterochemistry of a reaction Forcing a cis-product in the Pd-acetate catalyzed Heck reaction D. Tsvelikhovsky, J. Blum 9:1 1:1

33. Current /  A Electrochemical recognition of the imprinting molecule: Dopa Current (  A) L-Dopa D-Dopa Silica sol-gel thin films, 70 nm D. Mandler, S. Fireman

34. 6. Enzymatic reactions - enhanced stability

35. Protection from heat Very large shifts in the denaturing temperatures New, very mild entrapment method in alumina: Al(C 3 H 7 O) 3, pH 7.3, ultrasound OVA@alumina V. Vinogradov, 2014/5

36. Not only thermal stability, but increase in activity up to 60 o C … and stability to repeated cycles of heating to 60 o C and cooling Acid phosphatase@Alumina The activity at 75 0 C, is higher than at room temperature by about two orders of magnitude. # (AcP, 1) : Treatment of enzyme deficiency diseases

37. ACP@Alumina Arrhenius analysis The pre-factor of the entrapped enzyme A = 3.54. 10 14 sec -1 six orders of magnitude higher (!) than that of the free enzyme 4.34. 10 8 sec -1 60-70 o C

38. 7. Merging all of the above

39. Protection of an enzyme from strong oxidative conditions: Alkaline phosphatase protected from bromine H. Frenkel-Mullerad, R. Ben-Knaz, 2014

40. One-pot enzyme/catalyst pair 0.6 mmol acid, 2.5 mmol alcohol 0.01 mmol catalyst, 11U lipase F. Gelman, J. Blum

41. Conclusion Better materials based on chemistry Better chemistry based on materials