"This work is impossible to do" is correct. Here's a link for using adjectives + infinitives: https://learnenglish.britishcouncil.org/en/english-grammar/verbs/infinitive It's hard, actually, as a native speaker, to explain the difference, but "to do" is the infinitive form. "To be done" is not an infinitive ("to be" is an infinitive. "to be done" is not) and it feels very passive.

As for me - I would use: 1. It is impossible to do this work. 2. This work is impossible to be done.