Captive portal can be enabled and disabled by using the scheduler. With this captive portal scheduler, you can :
1. Either disable the captive portal so during that time period nobody needs to verify themselves using the captive portal WIFI.
2. Or you can disable the user login so for that period of time your users will not be able to login into the captive portal.
This will protect your WIFI when the workplace is closed.
This would ensure secure access at all times, as you can enable captive WIFI anytime.