It should be "심심한데요."^^' (심심하다 + ㄴ데요 ☞ 심심하 + ㄴ데요 ☞ 심심한데요) e.g. 심심한데요, 우리 영화 보러 갈까요? (informal, polite) 심심한데, 우리 영화 보러 갈까? (informal, not polite) = I'm bored, why don't we catch a movie? \^o^/

심심해요 or 심심하는데요. 데요 means nothing by itself, it is a part of the ending -ㄴ데 with the polite 요 attached to the end.