He could have the commerce department put TikTok on the Entity List, which would prohibit all US companies from doing business with them. It would be unprecedented though because putting a company on the Entity List is almost always tied to some actual criminal activity like trade violations or espionage (see HuaWei).
So there is away for him to do it, but TikTok could challenge it legally.
So there is away for him to do it, but TikTok could challenge it legally.