Remove below line and see if it is working or not
<urimapper:urimapping uri="/{pageName}" mappeduri="/RequestViews/Home.xaml" xmlns:urimapper="#unknown" />
Also it has nothing to do with the link control or button.
I can simply write
this.ContentFrame.Navigate(new Uri("/pagename", UriKind.Relative));
where pagename.xaml is the name of the page.
HTH.