Sulfur hexafluoride

Sulfur hexafluoride (SF6) is an dense, incredibly potent, long lived greenhouse gas, with a greenhouse potency of over 23,900 times that of CO₂, an atmospheric lifetime of 800–3,200 years, and a density almost 6x that of Air.

It is one of the Super Greenhouse Gases which have been considered to help Terraform Mars.

Sulphur hexafluoride is useful in greenhouses and other structures as a buffer gas, and to help maintain habitable temperatures. It has also been suggested as a means to terraform areas on mars, although using it at small scale to microterraform craters is more feasible.

SF₆ can be created readily using S and NaF, which are common byproducts of mining.

1. S + (2 + x) Br₂ + 4 KF → SF₄↑ + x Br₂ + 4 KBr (~20-80C)
2. 2 CoF₃ + SF₄ + [Br₂] → SF₆ + 2 CoF₂ + [Br₂] (~100C)

With a theorized step to regenerate the CoF₃ from HF or F₂ as needed, forming a loop.