All regular ground coffees are acceptable for Passover use when bearing an OU.

Decaffeinated coffee:
Coffee is often decaffeinated by means of ethyl acetate, which is derived from either kitniyot or chometz. Therefore, decaffeinated coffees are not acceptable for Passover unless specifically listed in the section of the Passover guide which contains items that to not require Passover certification.

Instant coffees often contain maltodextrin, which is derived from either corn (kitniyot) or wheat (chometz). Therefore, all instant coffees require special Passover certification unless explicitly mentioned in the section of the Passover guide which contains items that to not require Passover certification.