Hydrogen fuel cells are thought to be the best possible solution for our cars to run as clean as they can. Hydrogen, though, can only be stored in pressurized tanks, for the moment, and the mileage you get from a single fill is far from decent, or at least far from what we’ve been used to.
Metal organic frameworks (MOF) may have the solution to this issue the hydrogen has: rather than storing the hydrogen under pressure, they make it chemically bind onto them inside molecular “cages”, made from chains of carbon, oxygen and hydrogen atoms linked by metal ions. Then the hydrogen can be recovered by slightly heating the material, because the bonds between them are very weak.
MOFs have been made from different materials, but Fraser Stoddart of Northwestern University in Evanston, Illinois, and his colleagues found a way to make them from materials that are available right away, in your kitchen: sugar, alcohol, salt and water – unlike those made from oil derivatives like benzene compounds.
The sugary starch Stoddard adapted has a cubical molecular structure, with each side made of gamma-cyclodextrin, a ring of glucose molecules. This starch is used in many foods and pharmaceuticals, and is produced by bacteria, which makes it edible. “This arrangement is a previously unknown one,” says Stoddart. “The pore volume encompasses 54% of the solid body.”
Stoddard’s colleagues who tasted the substance said it resembles crackers.
The symmetry of the glucose rings is the secret behind creating the cages. If water and alcohol are also present, they join into cubes held together by ions of potassium (from salt) or a similar metal. The material they just created is finished when the water and alcohol are removed. Just a gram of it has a surface area of more than 1300 square meters – two houses with their garages and big gardens could fit in. Even though roomier MOFs had already been invented, this one is the cheapest yet.
Storing hydrogen in secure places and in high quantities may free us from gasoline and also from the pollution batteries do to the environment by deforestation and the toxicity that the lithium extraction methods come with. Burning it only produces water, and by the use of solar power, it can be restored from water. What else cleaner can there be?
