Is it permissible to pray for the deceased to repent, such as "O Allah, accept his repentance" or "O Allah, accept the repentance of the Muslim dead"?

The aforementioned supplication has not been reported in the transmitted supplications, but its meaning is correct and there is no harm in supplicating with it. However, it is better to replace it with the transmitted supplications, among them: "O Allah, forgive him, have mercy on him, grant him well-being, and pardon him. Make his abode generous and widen his entrance. Wash him with water, snow, and hail, and cleanse him of sins as You cleanse a white garment from impurity. Grant him a home better than his home, a family better than his family, and a spouse better than his spouse. Admit him into Paradise and protect him from the torment of the grave or the torment of the Fire."