The Dane is now going to play for the Swiss team for the next 18 months, as per the agreement.
Wolves confirmed the move on their official website.
Buur has been with the club since arriving from Aarhus GF in 2017.
He played for the under-23s and then moved up to the first team.
Given his lack of involvement this season, Buur will be hoping to get regular game time with Grasshopper in the coming months.