Isn’t that wishful thinking? Having automobiles which generate fuel for them while on the go! Perhaps it would need something like Alla Din’s lamp in Arabian tales? Engineers at University of Illinois at Chicago (UIC) have actually developed not a lamp but an artificial solar leaf that is a step towards this goal. There are no complicated intermediate processing stages. The leaves absorb carbon dioxide and release syngas that can be used as a fuel, and oxygen that purifies the atmosphere at the same time. Is it not going to be a really green automobile? 
Syngas (for synthesis gas) is a mixture of hydrogen, carbon monoxide, and traces of carbon dioxide. The name syngas came from the fact that this mixture is an intermediate stage in the production of synthetic natural gas, and other products like ammonia, and methanol (another alternate fuel). It can also be burnt directly, or converted to diesel or other forms of fuel. Can we turn atmospheric carbon dioxide, a major greenhouse gas, into fuel at a cost comparable with that of gasoline? That can make fossil fuels irrelevant, and thus contribute to energy security. It will also help check, and even reverse global warming.
What is the Alchemy involved? No Alchemy! It is a chemical process-photosynthesis precisely- but improved far beyond any previous artificial processes. The process is certainly green whether the ‘leaves’ are green or not in color. A major hurdle has been chemical reduction of CO2 (removing an oxygen from its molecule) for which very costly catalysts like silver were previously used. Engineers at UIC managed to find a much better catalyst in the form of a transition metal compound which is claimed to be twenty times cheaper, yet a thousand times faster.
Application possibilities can only be imagined. Do you think a solar forest of ‘trees’ with such leaves could form a health resort, while supplying cheap energy? On a small scale it could even be used in the home. A beautiful artificial tree can purify the inside air, enrich it with oxygen, and produce fuel for the burner. The idea could be particularly useful in space travel. The carbon dioxide released by breathing of astronauts could be converted back to oxygen while gaining fuel. We know forests breathe out oxygen. But now there is prospect of developing artificial solar forests which can breathe out not only oxygen, but also syngas, a fuel gas that has many end uses. And a major benefit is the effect on global warming. Not only is it free of GHG addition, it actually reverses GHG concentration by absorbing CO2 from the atmosphere. The invention could have far reaching effects on our life style, economy, and policies on environment. That is why the research is being supported by the U.S. Department of Energy and the National Science Foundation. The design has been tested using artificial solar light. But the designers are so confident of what they have achieved that a provisional patent application has already been made. For further information about the artificial leaf and solar energy efficiency, read this.