Ship-in-bottle synthesis and catalytic performances of platinum carbonyl clusters, nanowires, and nanoparticles in micro- and mesoporous materials

Ship-in-bottle synthesis of platinum carbonyl clusters, nanowires, and nanoparticles in micro- and mesoporous materials is described. Reductive carbonylation of Pt ions impregnated on NaY zeolite or on mesoporous silica FSM-16 leads to the selective formation of the Chini-type Pt carbonyl clusters. Decarbonylation of the resulting clusters yields naked Pt nanoparticles (diameter 1.0-1.5 nm) in NaY or in FSM-16. Similar Pt nanoparticles in FSM-16 are prepared by the direct hydrogen reduction of H2PtCl6/FSM-16 at 673 K, and in this case Pt particles in size of 2.5 nm are formed in the mesopores of FSM-16 (pore size 2.7 nm). In contrast, Pt nanowires (diameter 2.5 nm, length 50-300 nm) are obtained by the photoreduction of H2PtCl6/FSM-16 in the presence of vapors of water and 2-propanol. The Pt nanowires exhibit unique properties in CO chemisorption and magnetism due to their morphology in the mesoporous channels of FSM-16. In the water-gas-shift reaction, Pt nanowire/FSM-16 shows a higher catalytic activity than that of Pt nanoparticle/FSM-16. The Pt nanowires are chemically extracted from the mesopores using [NBu4]Cl in a mixture of benzene and ethanol. (C) 2001 Elsevier Science B.V. All rights reserved.