I have one non muslim friend. He asked me to take him to mosque for praying. He is not a muslim, so praying in a mosque by him is right or wrong? He wants to pray to understand whether it can give him peace or not.

Take him to imambargah where he can pray and In’Sha’Allah he will get peace and In’Sha’Allah he will be guided to right path and Allah will reward you.

Holy Quran 13:28
الَّذِينَ آمَنُوا وَتَطْمَئِنُّ قُلُوبُهُم بِذِكْرِ اللَّهِ ۗ أَلَا بِذِكْرِ اللَّهِ تَطْمَئِنُّ الْقُلُوبُ

Those who have believed and whose hearts are assured by the remembrance of Allah. Unquestionably, by the remembrance of Allah hearts are assured."