No.
The sump is simply a place to house your equipment.
Normally, people will use the sump as an area to place a skimmer, heater, refugium, filter socks, etc. The sump should not be considered a filter at all.
Many people will use a portion of the sump to grow macro algae, more live sand, even live rock. This would all be considered biological filteration.
Many people also use a portion of the sump to place a skimmer. This would be considered mechanical filteration.