Room-temperature ammonia formation from dinitrogen on a reduced mesoporous titanium oxide surface with metallic properties

Abstract

Mesoporous titanium oxide was treated with bis(toluene) titanium under nitrogen at room temperature in toluene, leading to a new blue black material possessing conductivity values of up to 10(-)(2) Omega(-)(1) cm(-)(1). XRD and nitrogen adsorption showed that the mesostructure was fully retained. Elemental analysis indicated that the material absorbed Ti from the organometallic, without any incorporation of the toluene ligand. There was also an increase of nitrogen from below the detection limit to 1.16%. XPS studies showed that the Ti framework was reduced by the organometallic and that the material had reduced nitride on the surface. There was also an emission at the Fermi level, suggesting metallic behavior. This was confirmed by variable-temperature conductivity studies, which showed a gradual decrease of resistivity with temperature. SQUID magnetometer studies revealed spin glass behavior with a degree of temperature independent paramagnetism, consistent with metallic properties. Solid-state (15)N NMR studies on materials synthesized in the presence of labeled dinitrogen showed that the source of the nitride was the reaction atmosphere. IR and (15)N NMR demonstrated that this nitrogen species was surface ammonia, suggesting that the initially formed nitride species had reacted with moisture imbedded in the walls of the mesostructure. The direct conversion of dinitrogen to ammonia is a very rare process and this work represents the first example of this process mediated by a molecular sieve.