Serendipity solves century-old chemistry problem

Ars Technica : Pure, crystalline magnesium carbonate, MgCO ₃, can be created by reacting CO ₂ and MgO at temperatures over 100 °C, but the compound’s structure inhibits its prodigious ability to absorb water. Finding a way to create the material in a more absorbent, naturally powdered form has been a goal of chemists for more than 100 years. Now, Maria Strømme of Uppsala University in Sweden and her colleagues have discovered how to do so. They were using a standard method of bubbling CO ₂ gas through a mixture of MgO and methanol, but had increased the pressure on the CO ₂ to three atmospheres. A reaction that was accidentally left running over the weekend resulted in a gel that formed when magnesium carbonate trapped the methanol inside it. Strømme’s team heated the material to 70 °C, past methanol’s boiling point. When the methanol evaporated away, the gel collapsed. What was left was a non-crystalline powder with an exceptionally high surface area per gram that made it more water-absorbent than the best current dessicants. After absorbing water it can be regenerated for reuse by heating it to just 95 °C.