Sulfur hexafluoride

Sulfur hexafluoride 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 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.