Disable the Nautilus Recent Files list
To permanently disable any recent files from showing up in the Nautilus Recent sidebar item, open the ~/.config/gtk-3.0/settings.ini
file with a text editor:
gedit ~/.config/gtk-3.0/settings.ini
and under "[Settings]", add the following lines:
gtk-recent-files-max-age=0
gtk-recent-files-limit=0
If this file does not exist, create it. Make sure the header says "[Settings]" and not "Settings". This is how the file should look after editing it:
[Settings]
gtk-recent-files-max-age=0
gtk-recent-files-limit=0
(there can be other items below these, of course).
To apply the changes, log out and log back in.
Copied from Webupd8 exercising (cc) BY-NC-SA WebUpd8 : Nautilus 3.6: How To Clear The Recent Files List (Or Disable It)