Is it permissible to spend Zakat money on mosque affairs?

The recipients of Zakat (definition) are specified in the verse from Surat Al-Tawbah (definition). Whoever disburses it outside of these categories has sinned, and their obligation has not been fulfilled. The category "fī sabīl Allāh" (in the way of Allah) is specific to jihad and its necessities, not to all good deeds. If it is possible to disburse Zakat for jihad, one should not deviate from it. If it is not possible, there are two approaches: either return it to the remaining categories or disburse it for things like building mosques and charitable projects. The accurate ruling is that if the need for such work is pressing and there is no other sufficient source, then it may be disbursed for it.