After the bad press that freon and chlorofluorocarbons (CFCs) have received over the years, it comes as something of a surprise to find that fluorine compounds are looking environmentally friendly. Dennis Curran of the University of Pittsburg in the US, and an increasing number of chemists, are realizing that fluorine-containing solvents can function well in place of dangerous chlorine-containing ones, but can also be very unreactive and hesitant to mix with other solvents. Acting almost like liquid teflon (another fluorine-containing compound), and easy to separate and recycle, they could greatly increase the cleanliness of industrial chemical processes.
Further reading
D Bradley 2003 Science 300 2022.