Here is an interesting article on transcritical CO2 heat pumps. I dislike the terms "organic vs. inorganic as my many hours in organic chem labs make me aware that anything with carbon in it is "organic".
Transcritical CO2 heat pump / Industrial Heat Pumps
These CO2 driven heat pumps are now in production and work incredibly efficiently. Even better than the original ammonia driven systems (incredibly dangerous) were very efficient.
Steve