In front of a home crowd Frampton never looked in trouble as he dominated his opponent, putting him down three times on his way to a 15th successive professional win.
Frampton was always able to stay ahead on points, never giving Molitor time and eventually his better work-rate wore his opponent down.
A flurry of punches in the sixth round forced the Canadian to his knees and it was clear he did not want to continue.
Molitor made it back to his feet but, with two minutes 21 seconds of the round gone, the referee called the contest off.
Frampton put his victory down to his preparation.
He said on Sky Sports 1: "I think it's just all down to hard work. I really pushed myself hard in training.
"I know I can hit hard - I've just got to land the shots. I didn't think he liked the pace that much - that's why I pushed so hard. I made him miss quite a lot (of punches).
"I was just on him the whole time - that was it really."
Frampton praised the crowd and promised them he planned to have more fights on home soil.
"I want as many fights here in Belfast as possible," he said. "The crowd was amazing. I'm not far from a world title. I will fight anyone."
Frampton's manager Barry McGuigan, the former world featherweight champion, pointed to the quality of Molitor.
"Steve Molitor is not a world champion two times over for no reason," he said.
"He (Frampton) just ground him down and eventually he nailed him.
"This guy is a fabulous young fighter. We intend to map it out and work towards a world title fight."