Go to Site
Settings>Site Content Type and create new content type.
Go to the library
settings of the document library and select advance settings. Choose yes on the radio button in allow management
of content type option and click ok.
In the library settings under content types click on add
from existing site content type option
Create a custom view and tick the make this default option
Under folder option select the desired content type and
click ok
Select the current default view and navigate to folder and
select in the top-level folder
option and click ok
