I know there is no API to schedule posts to Facebook Profiles, however some other social planners on the market do offer the ability to schedule a post on a facebook profile that will notify you on your phone at the scheduled time and have preloaded the images and text so you click Share to Facebook and its ready to post.

SocialBee is one such tool that can do it.

To make GHL be the one place for everything adding this would be gamechanger combined with the mobile app.