A　seed-directed　approach　to　synthesizing　FeZSM-22　zeolite　without　organic　structure　directing　agent　(OSDA)　was　developed　by　using　Fe-rich　diatomite　as　all　aluminum　and　iron　sources.　The　FeZSM-22　zeolite　with　optimal　crystallinity　and　purity　can　be　obtained　by　systematically　adjusting　feed　composition　and　synthesis　conditions.　Characterizations　show　that　FeZSM-22　zeolite　synthesized　with　OSDA-free　owns　high　crystallinity,　obvious　thin　needle-shaped　morphology　and　high　Bronsted/Lewis　acid　ratio.　Significantly,　when　used　for　n-octane　hydroisomerization　reaction,　its　derived　catalyst　exhibits　the　best　catalytic　performance　reflected　by　the　highest　selectivity　to　C-8　isomers　compared　to　the　two　reference　catalysts　prepared　based　on　a　Fe-containing　and　a　Fe-free　ZSM-22　synthesized　through　an　OSDA-directed　route　from　natural　diatomite　and　conventional　chemicals,　respectively.　This　work　provides　an　alternative　route　to　sustainably　synthesizing　heteroatomic　zeolites　with　high　performance.　(c)　2023　The　Chemical　Industry　and　Engineering　Society　of　China,　and　Chemical　Industry　Press　Co.,　Ltd.　All　rights　reserved.