Can a Wood Burning Stove use a stovepipe made of copper for a chimney?
You need to use a listed insulating stovepipe anytime combustible construction is penetrated. These pipes are also listed to be enclosed by construction. Thus it seems acceptable to me to install the listed stovepipe and enclose it inside a decorative copper tube.

For good measure, you should probably have some provision for venting the resulting annular space at the top and bottom of the copper tube.