He was duly promoted for his excellent performance at work.

duly 是 due 的副词形式，due 的意思是"应得的、适当的"，加上 -ly 变成副词后表示"适当地、理应地"。 duly promoted 表示"理应获得晋升"，强调晋升是基于正当理由和公平评估的结果。