he dedicated most of his time to charity work.

He dedicated most of his time to charity work.

他大部分时间都致力于慈善工作。

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dedicate表示把时间或精力等用在...，用在哪方面就用介词to。 dedicate的名词是 dedication,表示对某事的热诚和献身。
例：
Her dedication to education.她对教育的热诚付出。
He dedicated his life to science.他献身于科学。