Leading 2-0 from the first leg at Anfield, goals from Sadio Mane, Mohamed Salah, Roberto Firmino and Virgil van Dijk underscored an accomplished performance by Jurgen Klopp's side.
The Reds had been forced to survive an early bombardment in the saturated Estadio do Dragao, before Mane opened the scoring with a sliding effort - from Salah's scuffed shot - which was confirmed by VAR.
Salah stroked in a second after the break from a superb counter-attack before Real Madrid-bound defender Eder Militao pulled a goal back for the hosts.
Liverpool reasserted their authority though with close-range headers from Firmino and Van Dijk sealing an impressive victory.
Remarkably Porto had looked capable of capitalising on a sluggish Liverpool start until Mane's goal swung the momentum of the second leg back in the visitors' favour.
Until then Liverpool were the beneficiaries of errant finishing from the home side - with Moussa Marega notably failing to convert any of his five chances in the opening 20 minutes.
Liverpool will face Barca - who beat Manchester United in the last eight - in the first leg of their semi-final at the Nou Camp on Tuesday 30 April (20:00 BST).
BBCLast modified on Thursday, 18 April 2019