Zakaah should be paid immediately, and it is not permissible to delay it unless one has a valid excuse.
Among the excuses that have been mentioned by the fuqaha’ is when the money is not present and it is not possible to access it. This is an excuse which makes it permissible to delay payment.
Based on this, there is no sin on you if you delay paying zakaah until you are able to return to your country or you find other wealth which you can pay to those who are entitled to it. You do not have to borrow money in order to pay it.
Al-Mardaawi said in al-Insaaf (3/186): If he is unable to pay it (i.e., zakaah) from the nisaab because the wealth is not present, etc, then it is permissible to delay it until he is able to pay it. End quote.
It says in Fataawa al-Lajnah al-Daa’imah (9/398): It is not permissible to delay paying zakaah after one year has been completed except for a legitimate excuse, such as there being no poor people present at the time when one year is completed, or not being able to get the money to them because the money is not present, and so on. As for delaying it until Ramadaan, that is not permissible unless it is only a short time away, such as if the year is completed in the second half of Sha’baan, in which case there is nothing wrong with delaying it until Ramadaan. End quote.
It is clear that zakaah is a serious obligation and it is mentioned alongside prayer in the Book of Allaah. It is also a blessing that brings about growth in one’s wealth, so it should not be neglected under any circumstances.
And Allaah knows best.