Dunn, the World No 40 from Redcar, made the 147 in the fourth frame, potting 15 reds with blacks and clearing the colours. It's the 79th official maximum break in snooker history and the second of the season after Ronnie O'Sullivan's in PTC4. Dunn, who has suffered from the effects of kidney stones in recent months, goes through to face Adam Wicheard in the next round.
Wicheard beat Tony Drago 5-2 with a high break of 121 while in-form Peter Lines beat Simon Bedford 5-2.
Jamie Jones saw off Andrew Norman 5-2 with a top run of 95 while Jamie Burnett made 108 and 112 in a 5-2 win over Dechewat Poomjaeng.
China's Yu Delu came from 4-2 down to beat Barry Pinches 5-4 in a four-hour 37-minute tussle. The decider lasted 50 minutes and was won by Yu 67-12.
Ball by ball scoring and results from tournaments