Known as 'The Rocket', the mercurial O'Sullivan rattled home a red with his first shot of the game before going on to clear the table for the 16th maximum of his career, and his first in a competitive game since the 2018 English Open.
With the scores tied at three frames each, O'Sullivan did it again, coaxing the final red into the corner pocket with a superb stroke before potting the six remaining colours, prompting the 49-year-old and his fellow Englishman to shake their heads in disbelief at the end of the frame.
O'Sullivan, who became the second player to record two 147s in the same match after Welshman Jackson Page, will face Neil Robertson in the final on Saturday.