A　newly　synthesized　coordination　polymer,　[Cd(DMSO)(H2O)]3[Fe(CN)6]2　(CdHCF‐T),　based　on　Cd2+　and　Fe(CN)63−　ions　was　prepared　in　a　DMSO/H2O　mixed　solution　and　crystalized　in　the　trigonal　space　group　P‐31c.　This　novel　3D　structure　presented　an　interesting　single‐crystal　to　single‐crystal　transformation　when　the　coordinated　DMSO　molecules　were　replaced　by　H2O,　forming　a　well‐known　Cd　Prussian　Blue　analogue　(Cd‐PBA).　This　occurrence　is　a　rare　phenomenon　in　transition　metal　hexacyanometallates　and　may　provide　a　new　strategy　for　obtaining　new　structures　and　overcoming　the　difficulty　of　growing　single　crystals　of　Prussian　Blue　analogues.　Subsequent　gas　sorption　and　separation　investigations　based　on　the　obtained　Cd‐PBA　were　also　carried　out　to　evaluate　its　C2H2/CO2　separation　capability.