What should be done with the items that the brother bought during the second call to prayer for Jumu'ah, knowing that the purchase is considered void?

There is no harm in benefiting from what was purchased before the second Adhan (definition) on Friday because the majority of jurists hold that the prohibition of selling is related to the second Adhan. If the sale occurs after the second Adhan, jurists have differed regarding its validity. Some have declared it void (such as the Malikis and Hanbalis), while others have affirmed its validity, albeit with reprehensibility (karahah) or unlawfulness (hurmah) (such as the Hanafis and Shafi'is). Based on this difference of opinion, there is no harm in benefiting from these purchased items.