After using a purifier for two years pretty much non-stop (close to 24/7) I am pretty certain they don't help with dust at all. That's not why we install them, though.
How can you even search for this? Google results are not relevant to dust at all:
https://www.google.com/search?q=diy+air+dust+filter
This is a really strong example of how bad goog sucks for long-tail queries.
SEO spammed: https://www.google.com/search?q=home+dust+filtration+old+hou...
https://www.epa.gov/sites/default/files/2018-07/documents/re...
which cites this paper about deposition rates of different particle sizes:
https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=86094...
Try this: https://www.google.com/search?q=diy+air+%22dust+filter%22