Since those keys don't have acpi functionality, you can set the function manually through ccsm using xbacklight commands.
Run the following commands:
sudo apt-get update
sudo apt-get install compizconfig-settings-manager xbacklight
Now, press ALT + F2, type ccsm, and then press ENTER.
Next, enable the commands plugin and then click on the commands plugin.
Enter the command command line 0.
Click on the key bindings tab and click disabled on the command line 0 row.
Check the enabled box, click grab key combination and then press the key combo you would like to use to increase the brightness (fn + F6 for example). Click okay.
Finally, do the same for "command line 1" to set the brightness decrease except use the command xbacklight -dec 10
and use a different key combo (of course).
Thanks to this answer here provided by @TejasGhalsasi
You can set similar keyboard combos for other functions. The command to turn off wifi is:
nmcli r wifi off
and the command to turn wifi back on is:
nmcli r wifi on