Is it permissible to separate the two sermons and the two rak'ahs of the Friday prayer in order to collect donations for building a mosque?

If the interlude between the two sermons, or between them and the prayer, is for the preacher to admonish the people and encourage them to donate, then it does not cause harm. However, if the interlude is due to the preacher's silence and some of the worshippers collecting donations, then this causes harm if the interlude becomes long by common understanding. Continuity is a condition for the validity of the sermon and the prayer, so if the interlude becomes long due to speech, silence, or anything else, the sermon must be restarted.