I land in Beijing Capital Airport at 18:40 on a Friday night

And my next flight isn't until 13:45 the following day. I will be staying in a hotel inside the airport. Ideally, I would like to go checkout BJ as much as I can in the time that I have. Do you have any recommendations for something I can do in the evening hours after I am finished at the airport? I will be catching the Airport Express downtown. I know the last train back to the airport is at 22:30. If I were to stay out later than that, do you have other transportation recommendations on getting back to the airport after midnight?

Thank you so much for any feedback!

Devin