Danh prints on living leaves by sandwiching the leaf and negative between glass plates. I think it takes weeks to get good contrast. But I think the leaf is kept alive during that period.
You can probably extract chlorophyll and carotene from leaves, coat paper with that, and then perhaps see an image after it has been left in the sun with a negative for a good, long while or exposed with a photoflood for a shorter time. I don't know offhand whether it would be robust and permanent though, probably you need to at least UV coat it to keep some contrast and I guess the whole thing would turn a monotonous brown quite rapidly. Well... let's see, dried autumn leaves can stay red for ages, so maybe the carotene is the thing to target for printing, rather than chlorophyll.
Maybe I will try this myself.