Can I use static IP address as a component of 2 factor authentication for SFTP login?
The traditional factors used for MFA are:
But location ("somewhere you are") is also sometimes considered as a fourth factor - which could include a static IP address.
But your question shouldn't really be "can it be used as a component of MFA?", it should be "does it provide the security I need?". And that will depend on both the context of your application, and on exactly how trusted the IP address is.
The main problem with using an IP address is that it doesn't represent a person, it represents a network. And if that's a corporate network, it could have hundreds of people on, who all come from the same public IP address using NAT. It could also include an open guest wireless network that anyone near the building can use.
Is that acceptable for your security requirements?