7 hour layover in Beijing
 

I am flying from Bangkok to Boston and have a 7 hour layover in Beijing (6:50 am Arrival to 1:50 pm departure both on Hainan airline) and am wondering if that is enough time to leave the airport, and what you suggest doing? I realize I don't have the full 7 hours because of potential delays and leaving / coming back to the airport. If not, is there anything to see or do in the Beijing airport? Thanks! And any idea if I'll be able to see the Great Wall from my plane?

Sometimes when the plane flies over the Wall, the pilot will announce it.
You'll be out of the airport between 7h30 and 8h00 and you should be back no later than 12h30-12h45 (you need to clear exit immigration). That leaves you about 5 hours.
This is enough to go to the Great Wall. In your situation, you need to line up a driver ahead of time. It is about a one-hour drive from the airport to Mutianyu leaving 3 hours to get tickets, actually get to the top of the Wall, walk round and come back down. should be ok.
Alternatively, you can get on the Airport Express then the subway to visit somewhere around town. From the airport to the forbidden city is one hour each way. again leaving you with about 3 hours to walk around. Alternatively you can go to the area around the Drum Tower and walk around there. Or the Lama Temple and walk around there.
Her is a subway map: https://explorebj.com/subway/
You'll need local currency. Many ATMs at the airport.

12:30 to 12:45 sounds too short for a flight leaving at 1:50 for the US.

The airline says you need to be checked in 60 minutes before flight time, but it also says:

"However, to make sure you have enough time to go through security, please arrive three hours prior to departure when taking international flights and 120 minutes prior to departure when taking domestic flights."

Yes but he doesn't need to check-in.

Check that subway map. Beijing is massive in size and bigger than that in population. All you'll be able to do in that short time, and maintain your equanimity, IMO, is to take a walk.
I second the notion of subway to Dongzhimen, transfer to Blue line to Lama Temple. Then walk around the area, eat some local breakfast (don't expect to find many coffee shops), look around the temple and retrace your steps back to the airport.
You may find even getting the correct subway ticket ridiculous in its complexity, (esp if you cannot tell them where you want to go) and every subway station has baggage xray machines. Lots of police, with big guns, in Beijing. Hope you can be safe.

Hope you can be safe?
Wow, that sounds alarming. Subway x-ray machines are manned by kids who don't care. Never seen police with "big guns", maybe around government buildings or during special international events. They usually are just hanging out with other policemen smoking cigarettes and not paying attention to anything going on around them.
Beijing, or China, is among the safest places in the world to travel to.
subways are super easy to use with all signage in English. Go on YouTube and search for videos about "how to use the Beijing subway". There are many and you'll see how trivial using the subway is.

And, of course, there's a branch of Costa Coffee opposite the Lama Temple, and various other cafés in Wudaoying Hutong immediately west.

But I'd go to the Forbidden City (opens 8.3am--closed Mondays), although there's some complexity at the moment with ticket purchasing going to advance sales on-line. An English-language portal not necessarily requiring a local account is promised shortly.

Some suggestions as to how to get round it:

https://medium.com/a-better-guide-to...;-82b1079eed6b

If indeed staying around the Lama Temple, then also two neighbouring sights:

https://medium.com/a-better-guide-to...;-a40a9ec21ff3

https://medium.com/a-better-guide-to...;-291edccfd3c1

https://medium.com/a-better-guide-to...;-6d0f97556880

I see those links didn't come out properly. Here they are again:

Forbidden City: http://bit.ly/2kHygP4

Lama Temple: http://bit.ly/2rtOgZl

Confucius Temple: http://bit.ly/2rKwobR

Songtang Zhai: http://bit.ly/2sHFcnU

Thank you for all of your suggestions! I think I'll see how on time my flight is / how tired I am, and then try to go to the forbidden city if I'm up to it.

Keep in mind that the Forbidden City is HUGE - and once you're in it, you basically have to walk all the way through to get to the exit. It took us about 3 hours to walk through and see it... plus, there's the queue in the beginning to just get in, along with the security lines.

Also, it's typically really hot and sunny this time of year there - when we were there, it was over 90degF with no clouds at all, and very little shade in the FC - so you may get quite sweaty walking around before the flight to Boston... unless you have a place in Beijing where you can wash up, I feel sorry for the people sitting around you on the flight! ha!

Also know that depending on when you are going, the Forbidden city closes on Mondays.