title: Shape-selective sieving layers on an oxide catalyst surface.
abstract: New porous materials such as zeolites, metal-organic frameworks and mesostructured oxides are of immense practical utility for gas storage, separations and heterogeneous catalysis. Their extended pore structures enable selective uptake of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites contained within. However, diffusion within pores can be problematic for biomass and fine chemicals, and not all catalyst classes can be readily synthesized with pores of the correct dimensions. Here, we present a novel approach that adds reactant selectivity to existing, non-porous oxide catalysts by first grafting the catalyst particles with single-molecule sacrificial templates, then partially overcoating the catalyst with a second oxide through atomic layer deposition. This technique is used to create sieving layers of Al(2)O(3) (thickness, 0.4-0.7 nm) with 'nanocavities' (<2 nm in diameter) on a TiO(2) photocatalyst. The additional layers result in selectivity (up to 9:1) towards less hindered reactants in otherwise unselective, competitive photocatalytic oxidations and transfer hydrogenations.
authors.affiliation: Center for Catalysis and Surface Science, Northwestern University, Evanston, Illinois                 60208, USA.
authors.forename: Christian P
authors.initials: CP
authors.lastname: Canlas
authors.forename: Junling
authors.initials: J
authors.lastname: Lu
authors.forename: Natalie A
authors.initials: NA
authors.lastname: Ray
authors.forename: Nicolas A
authors.initials: NA
authors.lastname: Grosso-Giordano
authors.forename: Sungsik
authors.initials: S
authors.lastname: Lee
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Elam
authors.forename: Randall E
authors.initials: RE
authors.lastname: Winans
authors.forename: Richard P
authors.initials: RP
authors.lastname: Van Duyne
authors.forename: Peter C
authors.initials: PC
authors.lastname: Stair
authors.forename: Justin M
authors.initials: JM
authors.lastname: Notestein
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry; D002384:Catalysis; D046529:Microscopy, Electron, Transmission; D008958:Models, Molecular; D036103:Nanotechnology; D010087:Oxides / Q000737:chemistry*; D010777:Photochemistry; D016062:Porosity; D013237:Stereoisomerism; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry
chemical_list: D010087:Oxides; C009495:titanium dioxide; D014025:Titanium; D000537:Aluminum Oxide