You will almost definately need some kind of a framework, at a bare minimum your going to need some kind of template system, beacuse in the heady world of MVC separation of content from code is paramount.
As bjom states, you may likely end up writing your own mini framework that contains just the functionality you need.
You will also have to read up on configuring your web server too. Most MVC style web applications use url's like the following:
http://my.web.app/home/start
or
http://my.web.app/products/display/1
To achieve this your going to have to set your web server up to recognise the url format and then pass it to the appropriate php script. Under Apache this can be performed quite easily using mod_rewrite.
Just writing an MVC app on a page by page basis in pure PHP without making at least a mini framework, is going to be a big job, if you don't want to use any particular framework, i would at least suggest that you reuse smaller components of other frameworks, things such as the Smarty template engine and an inline editor for page creation.