Furniture scratching is a frustrating behavior unwelcome by most cat owners. In the cat's mind, he is simply marking his territory or sharpening his claws. For you, he is destroying an expensive piece of furniture. There are a couple of ways to diminish this behavior. The easiest, though painful for the cat, is declawing. A more humane method, which I prefer, is behavior modification including the use of deterrents, periodic nail trims and training your cat to use a scratching post.
For more information on why cats scratch in the first place and several ways to deter cats scratching on furniture, please click here.