soporific

Something inducing sleep, especially a drug.

The doctor prescribed a soporific to help the patient sleep.

And ancient soporifics—such as poisonous leaves and various opiate concoctions—were roughly as likely to kill you as they were to induce REM.

Something boring or dull.

Tending to induce sleep.

For we are not here to understand, as perhaps some have, that an author actually falls asleep while he is writing. It is true, that readers are too apt to be so overtaken; […]To say the truth, these soporific parts are so many scenes of serious artfully interwoven, in order to contrast and set off the rest;

It is said that the effect of eating too much lettuce is “soporific.” I have never felt sleepy after eating lettuces; but then I am not a rabbit. They certainly had a very soporific effect upon the Flopsy Bunnies!

Boring, dull.

The professor delivered a soporific lecture.

COP stands for conference of the parties under the UNFCCC, and the annual meetings have swung between fractious and soporific, interspersed with moments of high drama and the occasional triumph (the Paris agreement in 2015) and disaster (Copenhagen in 2009).