One of the problems with carbon dioxide is the strength of the carbon-oxygen bond. It is very difficult to break its bonds and free up the carbon for reactive chemistry. CO2 activation – the process of persuading oxygen-bound carbon to react – has therefore been a goal of chemistry for some years. A potential breakthrough has now come from researchers at Duke University in North Carolina, USA, who have engineered nanoparticles containing the precious metal rhodium that convert CO2 into methane via UV light. The methane could be used directly as a fuel or as a feedstock for reaction into further organic molecules.