it is +adi of sb to sth 与 It is +adj for sb to do sth 的区别有哪些,请指教,

of后面跟的形容词一般可以拿来修饰人的品格、特性之类的，例如 polite/ rude/ kind 等
用for的则不能，for表示做某事对你来说怎样，比如difficult/important/necessary等

用of的形容词是可以拿来修饰人的品格、特性之类的， 像It's clever/ polite/ rude/ kind/ brave...of you to ... 也就是可以说You are clever/ polite/ rude/ kind/ brave...
用for的则不能， It's necessary/ difficult/ important for sb. ...

it is +adj of sb to sth 与 It is +adj for sb to do sth 的区别
it is +adj of sb to sth
此结构中,形容词多是【修饰sb】,表明【人所具有的品质、特点】.常用的形容词有nice,kind,fine,honest,true,good,friendly,enthusiastic,warm-hearted,/bad,cruel,cold-blooded等.例如：
It's kind of you to say so.
可以转换为：You are kind to say so.
It's nice of you to help me.
It is +adj for sb to do sth
这个结构中,形容词多是【修饰sth】,表示【不定式短语内容所体现出的特点】.常用形容词有：important,unimportant,difficult,hard,easy,necessary,unnecessary ,helpful,useful等.
例如：
It's important for us to learn a foreign language .
可以转换为To learn a foreign language is important.

it is +adi of sb to sth 中的adj与 It is +adj for sb to do sth 中的adj是不同的
it is +adi of sb to sth 中的adj是修饰人的好坏 如：kind，goodness
而It is +adj for sb to do sth 中的adj是作用在人或物上 如：necessary