Keeping water away: Syngas, a mixture of carbon monoxide (CO) and hydrogen, allows nonpetroleum resources such as biomass and natural gas to be converted to chemical products through Fischer-Tropsch synthesis. However, for the production of olefins, a key feedstock for other chemicals, about 50% of the CO is transformed to carbon dioxide and methane. Xu et al. decreased the selectivity for these undesired by-products to under 25% by modifying their catalyst, nanoparticles of iron doped with manganese and coated with a silica, with methyl groups (see the Perspective by Xie). This hydrophobic surface shortens the retention time of water on the catalyst surface to avoid the unwanted side reactions, and also suppresses oxidation of the metal carbide catalyst that forms under reaction conditions. Science , this issue p. 610 ; see also p. 577