关于
guān yú
Expressing "about" with "guanyu"
关于 introduces a topic, and the phrase normally opens the sentence.
关于 + Topic，⋯⋯
How it works
关于中国历史，我知道的不多 — as for Chinese history, I don't know much. The topic is set up first, then commented on.
It also modifies nouns: 一本关于中国的书.
对于 is a near neighbour that frames an attitude towards something rather than a subject matter.
Examples
guān yú zhōng guó lì shǐ, wǒ zhī dào de bù duō
关于中国历史，我知道的不多。
As for Chinese history, I don't know much.
zhè shì yì běn guān yú zhōng guó de shū
这是一本关于中国的书。
This is a book about China.
guān yú zhè jiàn shì, wǒ men míng tiān zài tán
关于这件事，我们明天再谈。
As for this matter, let's discuss it tomorrow.