one way ticket HKG-PEK and the continue on the inbound flight of the return ticket PEK-VIE

Please, can you tell me if I can plan my travel following way: I have a return ticket Vienna - Beijing and single entry Chinese entry permit. From Beijing I would travel south and by the end of my China`s mainland trip I would go to Hongkong (that would probably make my chinese visa invalid, cos I left the country), then fly back to Beijing on the last day morning, use visa-free transit to have a last look around Beijing and after midnight hop on my return flight to Vienna after midnight. Would Visa-Free Transit work for me? Thank you