Murphy, whose only victory in the tournament came a decade ago when he defeated Robertson in the final, set the tone for a high-quality contest with a 90-point break in the opening frame.
When the Australian responded with a break of 79 in the next round, it briefly looked as if a classic contest awaited him.
However, that was not to be achieved with Murphy pressing the pivotal fifth frame with a point on the black and barely missing the bowl once between the balls.
When he did, his black spot removed in the sixth frame, he was punished severely as his opponent built a break of 108 to get back within two frames.
Robertson was unable to mount the kind of recovery that enabled him to come back from 5-1 down to John Higgins in the first round and Murphy was seen wanting at the end as he came agonizingly close to the ninth 147 of his career.
Robertson added: “I couldn't believe it. It was a real shame for everyone who saw it. I felt so bad for Sean.”
“I played great and when two players play really well, the smallest of margins can be the difference. You have to take your hat off to Sean for how well he played.”
