How about a picture. There are several plants commonly called moonflower.

Any plant, even a sun lover, will wilt if taken from indoors to full sun without hardening off. They need a gradual transition from inside to outside.

the moon flowers i am thinking of.. end up huge vines by late summer.. and should be in the ground by now ...

at best.. indoor light from a window is less than 50% strength of sunshine ... so you have to harden them off to direct sun ... acclimate them.. if you will ... a few days in shade.. then a few days in early or late sun.. etc.. a slow process ..

i also suspect.. your pot isnt big enough.. to hold the water.. a plant in the sun needs to cope with such ... it might be time to repot .. or plant in mother earth ... and if you do that.. thats a week in the shade to get the roots working .. before it goes into more sun ...

ken

Moonflower vine, Ipomoea alba. You're doing the right thing.