Update PCSX2. Stable 1.6.0 is from 2020 – it does not support CHD. Switch to a Nightly build (1.7.5+).
The adoption of CHD has been rapid because modern emulators are built to handle it. ps2 chd roms
Unlike standard compression formats like ZIP or RAR, an emulator can read a CHD file directly without extracting it to your hard drive first. This eliminates the need for temporary storage space and extra loading times when launching a game. Why Use CHD for PS2 Games? Update PCSX2