Future Directions in Catalysis Research: Catalysts that Function at the Nanoscale. Harold Kung Northwestern University

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1 Future Directions in Catalysis esearch: Catalysts that Function at the Nanoscale arold Kung Northwestern University

2 Need for site-specific characterization technique: By monitoring the motion of portions of a protein that constitute uman cyclophilin A (CypA) duirng cis/trans isomerization of peptidyl-prolyl, and correlate it to the catalytic reaction and the binding of the substrates, it is possible to identify definitively where are the active and binding sites. E. Z. Eisenmeser, D.A. Bosco, M. Akke, and D. Kern, Science 295 (2002) It has been shown that metal-metal and metal-oxygen bond lengths changes during hydrogenation of propene. A. M. AG, J. F. DZAK, F. S. LAI & B. C. GATES, Nature, 415 (2002) 623.

3 uman cyclophilin A (CypA) duirng cis/trans isomerization of peptidyl-prolyl E. Z. Eisenmeser, D.A. Bosco, M. Akke, and D. Kern, Science 295 (2002) 1520 Nature of active site Binding sites elative Locations of active and binding sites specifics of cavity

4 Adsorption and selectivity Two Co(III) ions in CoP-18 at the desired distance apart in Co/P = 0.1 samples. CoP-36 of larger pore structure and shape, produces much more 3-ol and 3-one. aja and Thomas, J. Molec. Catal. 181 (2002) 3 exane ( ) xidation 1.5 MPa air, 373 K, 24 h, Selectivity % eactant Conv. 1-ol 1-ald 1-acid 1,6-acid 1,6-ol/al 2-ol/one CoP-18 (Co/P=0.04) C % CoP-18 (Co/P=0.1) 9.3% CoP-36 (Co/P=0.04) 5.2% CoP-34 (Co/P=0.1) 7.9% J.M. Thomas, et al. Nature 398 (1999) 227; Angew. Chem. Int. Ed. 39 (2000) c

5 ligomer with Metal-oxygen Backbone and Defined Sequence And Structure Si

6 Challenge: Incorporation of active sites and binding sites at designed locations. Challenge: Controlled but arbitrary cavity and channel shapes. Challenge: Flexible cavities, pores and windows to cavities.

7 (Ppy-M + ) + A - (Ppy-M + A - ) E. Smela,. Inganas, I. Lundström, Sci. 268 (1995) 1735.

8 From Scientific America, November 27, 2000.

9 Molecular hinges to control accessibility of active sites P P Active At rest

10 Nanoreactor for high selectivity + X +

11 Mesoporous benzene-silica S. Inagaki et al, Nature, 416 (2002) 304 A l Single-walled carbon nanotube Single-walled metal-oxygen nanotube Control of nanoreactor wall properties 4 nm

12 Molecular Switching via edox 1. eduction by ascorbic acid 2. xidation with ammonium persulfate 3. Conformational change monitored by circular dichroism - S. Zahn and J.W. Canary, Angew. Chem. Int. Ed. 37 (1998) 305

13 J. ebek, Jr. Acc. Chem. es. 17 (1984) 258 V. Balzani, A. Credi, F.M. aymo, J.F. Stoddart, Angew. Chemie Int. Ed. 39 (2000)3348

14 V. Balzani, A. Credi, F.M. aymo, J.F. Stoddart, Angew. Chemie Int. Ed. 39 (2000)3348

15 Points: 1. Nanotechnology assists in achieving control of active sites and site environment 2. so offers opportunities to construct nanoreactors that provide specific chemical funcationalities to enhance reaction selectivity 3. Future challenges include: Controlling locations of active sites and binding sites Controlling nature of active sites Flexible openings and cavities Incorporation of molecular machines in reactors eliable methods for mass production

16 ther points: ow Does catalysis benefit from long-ranged ordering of porosity? What new developments are needed in Catalysis as enabling technology for other fields of nanotechnology. Can catalysis be used to alter the order of assembly?