Alternatively, for $2 trillion, you could probably solve cold fusion and synthesis of liquid fuels, making the Middle East's oil wealth effectively irrelevant.
Cold fusion is basically impossible according to the laws of the universe as we understand them today. You'd have to do some sort of major discovery about the fundamental physics to do cold fusion. It's unclear (and IMHO, very unlikely) this will ever happen. It's very much not a money issue, it's a "we need to wait on some Einstein to make a major discovery of an unknown nature" issue, except that we don't know if that's even possible.