Oh goodness me, a sacrifice that isn't the queen...
Important things are: (1) To prevent Black replying with Rxe1+, so White's move must be a check. (2) It must attack both g5 and h6. (3) The queen cannot do this from e3 or d2 because Black can reply f5-f4.
If White tries Qf4+, then Rxf4 leaves no checkmate.
So, 1. Bf4+. Black can capture with either rook from f1 or bishop from c7, but White then has 2. Qg7#
I noticed that the queen and Rf1 could check, this I'd had to begin with a check. When all checks are successfully refuted a sacrifice is the only thing left. Not the queen... this led me to the solution... with a little bit help from my friends.
If White tries Qf4+, then Rxf4 leaves no checkmate.
So, 1. Bf4+. Black can capture with either rook from f1 or bishop from c7, but White then has 2. Qg7#