自命清高

zìmìngqīnggāo
  1. to think of oneself as high and pure (idiom); smug and self-righteous
  2. holier-than-thou

CEDICT

to consider oneself morally superior to others and refuse to associate with others

Wiktionary

自认为清雅高洁，不屑与世俗同流合污。

重編國語辭典

Entry Composition

1 自命 zìmìng to consider oneself to be (sth positive)
2 清高 qīnggāo
  1. noble and virtuous
  2. aloof from politics and material pursuits