  Type 5A molecular sieves (MS) have been demonstrated to remove radon from
SF$_6$ gas. This is important for ultra-sensitive SF$_6$ gas-based directional
dark matter and related rare-event physics experiments, as radon can provide a
source of unwanted background events. Unfortunately, commercially available
sieves intrinsically emanate radon at levels not suitable for ultra-sensitive
physics experiments. A method to produce a low radioactive MS has been
developed in Nihon University (NU). In this work, we explore the feasibility of
the NU-developed 5A type MS for use in such experiments. A comparison with a
commercially available Sigma-Aldrich 5A type MS was made. The comparison was
done by calculating a parameter indicating the amount of radon intrinsically
emanated by the MS per unit radon captured from SF$_6$ gas. The measurements
were made using a specially adapted DURRIDGE RAD7 radon detector. The
NU-developed 5A MS emanated radon up to 61$\pm$9$\%$ less per radon captured
(2.1$\pm$0.1)$\times 10^{-3}$, compared to the commercial Sigma-Aldrich MS
(5.4$\pm$0.4)$\times 10^{-3}$, making it a better candidate for use in a radon
filtration setup for future ultra-sensitive SF$_6$ gas based experiments.
