A formal heretic is defined as someone who deliberately doubts or denies a revealed truth of the Catholic faith. Look at the quotes from Francis on Francisquotes.com and you will see Francis is certainly a formal heretic 20 times over.
Material heresy is due to the outcome of ignorance, and looking at the quotes on that website, it's obvious that Francis cannot claim ignorance on subjects like promoting atheism, doubting the Blessed Trinity, approving of cohabitation, approving of contraception, approving of ecuмenism, etc. etc. Anyone who claims he is only a material heretic is only kidding themselves.