All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
If the husband gave the jewelry to his wife as a loaned item, it is permissible for him to take it back regardless of whether he keeps his wife or divorces her.
However, if he gave it to his wife as part of her bride's money or as a gift, he has no right to claim it after the divorce.
If the wife is requesting divorce without any harm caused to her by the husband, it is permissible for him to refuse to divorce her. He may offer to divorce her in return for her bride's money, part of it, or any other compensation paid out from her wealth.
However, if the wife requests divorce due to harm caused to her by her husband, she has the right to refer the matter to the judge (at a Sharee‘ah-court) to issue a judicial divorce, whereupon she would be entitled to her bride's money and all the other rights sanctioned by the Sharee‘ah for a divorced woman. The husband, in this case, has no right to claim any part of her dowry or anything else he had gifted her.
Allah knows best.