Use:
bash -c '
In the case of a the _i3 keybinding_ this translates to:
bindsym $mod+F8 exec i3-sensible-terminal -e bash -c 'xprop & read line'
**Also** – kinda _workaround_ – also could be:
bindsym $mod+F8 exec i3-sensible-terminal -e bash -c 'xprop & sleep 60'
The terminal is kept awake – _by sleeping (o;_ – for 60 seconds with the `& sleep 60` command.