Which documents recently released by the CIA demonstrate the U.S. intervention in Iran in 1953 was over communist fears not economic (oil) motives?
I do not know of any documents that have been released very recently that prove this. There was a report that was written in 1954 by one of the CIA people who was involved in the operation. It was released in 2000. That report, which can be found in the link below, at least claims that the US intervention was caused by a fear of communism rather than by economic motives. For example, there is a passage that reads
... it was estimated that Iran was in real danger of falling behind the Iron Curtain; if that happened it would mean a victory for the Soviets in the Cold War and a major setback for the West in the Middle East.
This passage shows that, in a document prepared for internal CIA records, the main reason given for overthrowing Mossadeq was a fear of giving the Soviets a win in the Cold War. This does not conclusively prove that this was the reason for the intervention. It may have been the true reason for the intervention, but the document does not prove that.