I'd like to know the Catholic perspective on whether art with the portrayal of persons in the nude is moral. Such art is frequently found in Catholic churches, especially in Europe. If it is within the bounds of Catholic morality, how is it different from

Since, as you mention, nudes are common to the Western cultural tradition and such artworks are found in Catholic churches around the world, that is a good indication that the Church does not consider nudity in art to be inherently immoral. As a basic rule of thumb, the purpose of pornography is to titillate. The purpose of nudity in legitimate art is to portray God's creation, of which man is the apex in the material world, and thereby to elevate the mind to God and to glorify him.