Graphene is special in lots of ways; one-atom-thick sheets of bonded carbon atoms, it's the strongest material known, and it has important electronic properties. Its smallest possible bond is about 0.14 nanometers, so it can be hooked together in very tiny configurations, although this is difficult to do. At MIT, materials scientist Jeffrey Grossman and graduate students have been running computer models to determine the right pore size. They may need to bombard graphene sheets with helium ions to make properly-sized pores, or perhaps some nanostructuring techniques to grow the right size sheets. The pores may also need to be treated with other chemicals to make them interact with water molecules.