From the Sofitel Liberdade Lisboa, the nearest train station for Porto is Sta. Apolonia, which is also the terminus for trains to and from Porto from Lisbon.
If you have a lot of bags, I would counsel a taxi which should not cost more than a few euros.
The hotel is close to Avenida Metro station, which is on the Blue Line which runs straight to its terminus at Stª. Apolonia. It is a 10 minute run to Stº. Apolonia.
