1- Darauf, dass er heute kommt, freue ich mich.
2- Darauf freue ich mich, dass er heute kommt.
I know that we can use instead:
Ich freue mich darauf, dass er heute kommt.
Alle drei Sätze sind richtig.
In fact, all three sentences are perfectly correct. The third form would be the one most often found in textbooks, Katarina, which is probably why only that one seems correct to you. Whether and if you'd use one of the others would depend largely on context. For example, you might use this form when replying to a negative question like "Freust Du Dich denn gar nicht, daß er kommt?"
Thank you all for your answers
Mauro, I was in doubt whether especially the second one is right
I would say that the first two sentences are just wrong, but maybe someone will correct me.