Yes, you can using the Timed Access settings in AirPort Utility.
Macintosh HD > Applications > Utilities > AirPort Utility
Click on the AirPort Extreme icon
Click Edit
Click the Network tab
Enter a check mark next to Enable Timed Access
Click the Timed Access button

In general, you will enter the wireless MAC Address of the iPhone, along with daily times that the device will be allowed to connect to the network.
Example.....
Daily.....between......8 AM and 9:30 PM
Or, another example might be......
Weekdays.....between 8 AM and 9:30 PM
Saturdays......between 8 AM and 11 PM
For specific details on how to set up Timed Access......
Click the Help Menu at the top of the screen
Click AirPort Utility Help
Click Setting up a Wi-Fi network on the left
Click Control when a user can access your network