AC2300 supports wireless mac filtering. Put your devices to the white list, and other wireless devices can be blocked.

I don’t see a way to get to the whitelist in the tp-link UI when it’s set up as an access point and DHCP is off. Where would I set that up? There is no Security tab when it’s in that mode.

But does it support a whitelist in access point mode? I don’t see any way to add a whitelist since the security and DHCP options aren’t visible in access point mode.

Did you use Mac filer or wireless Mac filtering? Wireless Mac filtering can't control C2300 which is wired connected to the main router.
I believe that you have add the C2300's Mac address to the white list of the Mac filter, otherwise the devices connected to C2300 can't get internet at all.
If this case, the Mac filter can't block some certain devices and allow some other devices connected to the C2300.

I have the Archer 2300 connected with a hard wire to the main router and configured to be used as an access point only. The Archer is working and I can get internet access through that router for all the devices that are connected to it. I am certain that is true since my main router has never delivered a wireless signal to the rooms upstairs and the signal is stronger there with the Archer installed. Because it is hard wired I do not have the MAC for the Archer in the whitelist (Access Control list) of the main router. All of that works. I can secure my network with WPA2-PSK+WPA-PSK security and that also works but I have always backed that with access control. The main router still functions using its access control list, i.e., if I shut the Archer off any devices that are not in the main router's access list are kicked off the network. With the Archer on any device with the proper network name and password are allowed access, indicating the access list on the main router is not used by the Archer. Since the Archer is in Access Point mode there are no options in the UI to configure further security - which means there is no place to add a whitelist. I had hoped the Archer would defer to the control list from the main router but does not appear to be the way it works so I am looking for a way to add the same whitelist to the Archer as I have configured in the main router. I just don't see a way to do that.

You can contact TP-Link support to see if they can duplicate your issue and find a solution for you.

Page 22 of the user manual specifically says parental control, NAT and ,Qos not supported in access point mode is that what you are trying to figure out ?

I'm also trying to use the Wireless MAC filtering function and I'm not finding it in the menu, nor in router mode, nor in access point mode. It seems that the TP Link forgot to add this function in C2300.

Tallboy wrote

Page 22 of the user manual specifically says parental control, NAT and ,Qos not supported in access point mode is that what you are trying to figure out ?

That's what we're talking about. The C2300 does not exist in the menu.

The below attachment shows using MAC filters in C2300 router mode. This options will not be available in access point mode hope its clear.