The problem is that over time the atmosphere would vaporize into space from the hot side so you will get a barren rock like Mercury. There's always a liiiiitle

The problem is that over time the atmosphere would vaporize into space from the hot side so you will get a barren rock like Mercury. There's always a liiiiitle rotation, so even any frozen gases on the cold side would eventually rotate into the sun and be heated to escape velocity.