No abstract

The direct low-temperature oxidation of methane to methanol is demonstrated on a highly active homogeneous molecular catalyst system and on heterogeneous molecular catalysts based on polymeric materials possessing ligand motifs within the material structure. The N-(2-methylpropyl)-4,5-diazacarbazolyl-dichloro-platinum(II) complex reaches significantly higher activity compared to the well-known Periana system and allows first conclusions on electronic and structural requirements for high catalytic activity in this reaction. Interestingly, comparable activities could be achieved utilizing a platinum modified poly(benzimidazole) material, which demonstrates for the first time a solid catalyst with superior activity compared to the Periana system. Although the material shows platinum leaching, improved activity and altered electronic properties, compared to the conventional Periana system, support the proposed conclusions on structure-activity relationships. In comparison, platinum modified triazine-based catalysts show lower catalytic activity, but rather stable platinum coordination even after several catalytic cycles. Based on these systems, further development of improved solid catalysts for the direct low-temperature oxidation of methane to methanol is feasible.

An intimate mixture of CuO/ZnO nanocrystals was prepared by an easy sol-gel synthesis (precipitation in methanol by hydroxide in the presence of a silane). The organic substituents of the silane were almost completely removed by a subsequent photochemical oxidation. The resulting amorphous SiO 2 prevented the growth of the catalytically active particles to larger crystals. The coating layer of silica can easily be penetrated by gaseous reactants, as shown by the high spe-