How Can I execute a shortcode in a iframe with srcdoc attribute?

Hi, I need load a form inside an iframe. The form I can load with this shortcode: [wpuf_form id="106"] but I don't know how put this to get load inside an iframe. This is the code that not work for me:

<iframe srcdoc=" '.do_shortcode('[wpuf_form id="106"]').' " width="100%" height="400px" frameborder="0"></iframe>

Best regards