The phrase "an unprecedented request" is correct and usable in written English.
You can use it to describe a request that is unique or has never been made before, often implying that it is significant or surprising.
Example: "The committee received an unprecedented request for funding from a new organization that aims to tackle climate change."
Alternatives: "a never-before-seen request" or "an extraordinary request."
It was an unprecedented request that goes to the heart of the principle of open justice.
It was an unprecedented request for an unproven, independently produced title.
It was an unprecedented request: foundations had never bailed out a city before; it wasn't what they did.
We had guaranteed an unprecedented request from our government for £10m of our own money to make it happen.
"This is an unprecedented request that warrants further briefing," the presiding judge, Colleen Kollar-Kotelly wrote of the A.C.L.U.'s motion.
The Maryland elections board sought advice from state Attorney General Brian E. Frosh (D) on how to respond to what elections experts called an unprecedented request.
It received a virtually unprecedented request from Google Lunar X Prize contestants to explore how to visit the six Apollo landing sites and several unmanned Surveyor spacecraft from the 1960s.
Journalists attending the event were required to "rent" the Wi-Fi for $200 for five devices – not an uncommon or unprecedented request.
The unprecedented request from a eurozone member state comes barely 10 days after the emergency standby loans were agreed.
The report from the UNESCO advisory bodies recommended the 38th world heritage committee meeting in Doha, Qatar, next month "did not approve" the Abbott government's unprecedented request for a "minor boundary modification" that would delist 74,000 hectares of forest added to the Tasmanian wilderness world heritage area less than a year ago.
Culture tells us how to respond to an unprecedented service request.
