VATICAN CITY — Pope Francis called for structural renewal in the Catholic church to keep up with the times, although advising future priests and nuns to shun costly trappings like the latest smart phones so they can use more resources to help the poor.

Francis has been waging a campaign to root out corruption and power plays in the Vatican’s bureaucracy and to keep sight of what is essential in the church he was elected in March to lead.

The Argentine-born pontiff offered the encouragement for renewal in a homily during Mass at the Vatican City hotel where he lives. Francis told Catholics “not to be afraid of renewing some structures” to accord with “the places, the times” and the people, but he didn’t specify what needed to be changed.

He said, “In Christian life, even in the life of the church, there are ancient structures, transient structures: It is necessary to renew them!”

Later, he gave an off-the-cuff lecture to a Vatican auditorium full of seminarians and novices, and to thunderous applause, told the future priests and nuns to keep “freshness” and “joy” in their lives, and took to task seminarians and novices who “are too serious, too sad. Something’s not right here,” Francis told his rapt audience. “There is no sadness in holiness,” said Francis, saying that such clergy lack “the joy of the Lord.”

“If you find a seminarian, priest, nun, with a long, sad face, if it se ems as if in their life, someone threw a wet blanket over them,” you should conclude “it’s a psiatric problem, they can go, ‘buenos dias,’” Francis said, opting for a word in his native Spanish to indicate those clergy are not suited for their vocations.