You can record the grant you've received by depositing the funds and use other income as the source of account for deposit. Then, write a check or enter expense when it's time to reimburse.
This needs you to create accounts that are associated with each transaction. That being said, I'd recommend consulting an accountant to ensure that the accounts made are set up correctly. Here's how to create an account:
Go to the Accounting menu and select Chart of Accounts.
Click the New button.
Enter the details of the account.
Select Save and Close.
I've added these article that may help you in the process: