～のに、…のに — although / even though
Although のにContrary to expectation: “although A, (unexpectedly) B”.
約束したのに、彼は 来ませんでした。
やくそくしたのに、かれは きませんでした。
Even though he promised, he didn't come.
のに joins two clauses where the second is contrary to what the first leads you to expect, often with a nuance of surprise, dissatisfaction or regret. Na-adj/noun add な: 元気なのに.