That is refrigerant dependent. For example R744 (plain old CO2) works well efficiently down to -4F, -20C and down to -40C/-40F just with some efficiency drop.

Main issue is CO2 needs a constant high pressure heat pump system, since it needs to be highly pressurised to be fluid at all. In ambient it sublimates (goes straight between gas and solid aka dry ice).

However that is a solved issue. Working CO2 heatpumps are off the self commercially available these days. Just still little more expensive as I understand. However prices should come down with production economies of scale, upon CO2 taking over due to pollution, toxicity, flammability, green house considerations. He nastier chemicals weren't used for being all the ways superior, but due to it being easier to make the heat pump units (be they running in heating or in cooling) due to lower pressure requirements.

Since CO2 and ammonia were the original refrigerants. Used in large ice production facilities early on, where their specific needs weren't issue even for earlier technology. Large, purpose built, stationary industrial facility had no problem accommodating the needed massive pressures by just really massive and heavy pipework.

However these days the propeller head people developed micro channel tubing and heat exchangers to keep the high pressure CO2 in control.