capturing packets from offline devices

[ItsLeepq]

Hi all, I am quite new to this and played around a little with the ESP32 board. I am using a person counter code from this guy: p99will's code

I edited the code to remove the Adafruit OLED part and it works fine. However, I want to ask all of you if there is a way to get mac addresses from devices with their WiFi switched off. As seen from this paper: pdf document which shows WiFi frames being sent out devices with WiFi switched off. I wanted to capture those devices mac addresses as well. So how do I do that? Please help me.

Thanks in advance!