Last Updated: 25 Jun, 2020     Views: 154

You're thinking of the Academic Phrase Bank, provided by the University of Manchester. You can get to it from the page on Academic Language of the Writing Guide, under the Writing Process tab, but here's the direct link:

http://www.phrasebank.manchester.ac.uk/

It's a handy little thing, that can help you shake up your sentences while still sounding "academic".