Assuming that you had Find My enabled on the iPhone – and that it is still enabled, you could log in to your Apple ID account, mark the phone as Lost, and request that the phone Erase itself.
Mark a device as lost in Find My on iPhone - Apple Support
Once the phone learned of these requests (which would require power and an Internet connection), it would enable Activation Lock – essentially "bricking" itself, and making itself useless to anyone who did not know the right Apple ID credentials to unlock it. As long as you did not remove the phone from the list of devices that are associated with your Apple ID, or disclose your credentials, it would forever remain a "brick".
You might not get your phone back, but you could "brick" it for the thieves (and their customers).
Issue: The thieves probably know about Activation Lock, too, and they might have disabled Find My, or removed the phone from the list of devices associated with your Apple ID, before you could re-secure your Apple ID. If they were able to do that, then it will be too late to "brick" the phone in that way.
If the thieves weren't able to disable Activation Lock in time, you or people you know may get messages and phone calls from the thieves who will be pretending to be from "Apple Support" (or some such) and saying that they want to reunite you with the phone. These are "phishing" messages – lies intended to get you to release the Activation Lock, to give them the information needed to release it, and/or to help you scam you in some other way.