It is well known that Zakāt is to be given to particular categories of recipients. Allāh says:
“Zakah expenditures are only for the poor and for the needy and for those employed to collect it and for bringing hearts together [for Islām] and for freeing captives [or slaves] and for those in debt and for the cause of Allāh and for the [stranded] traveler – an obligation [imposed] by Allāh. And Allāh is Knowing and Wise.”
However, a common misconception is that Zakāt is the only obligation upon one’s wealth. This results in people mistaking the importance of a charitable project—such as building a mosque, sponsoring students, training leaders, and so on—with the validity of donating Zakāt towards them. There is a very important distinction between the importance of a particular charitable goal, and the recipients of Zakāt.
Extolling the importance of a particular charitable goal only goes to show that it may be obligatory upon the Muslims to pay sadaqa towards those goals, not trying to kill two birds with one stone and using their Zakāt to pay for what is already an obligation for them. This is why the jurists were careful to produce principles such as ‘one obligation should not be used to strike off another’, and ‘one should not benefit from the payment of one’s own Zakāt’.
Thus the scholars explicitly prohibited people paying Zakāt towards those they are already financially responsible for such parents and children.
To reiterate, there are many worthwhile—and possibly obligatory—charitable projects and goals that we all should contribute towards depending on our means. However, Zakāt is emphatically a distinct obligation that should not be mixed up with other obligations, with its categories being fixed. This is a pillar of Islām so should not be taken lightly, and I advise all Muslims to put themselves on the safe side by ensuring their Zakāt is paid and distributed in strict accordance with the Sunnah, whilst separately paying whatever they can for the other worthwhile projects in ones area and beyond with other types of sadaqa.
 Al-Qur’ān 9:60