This　study　aimed　to　provide　new　insights　into　the　mechanism　of　Cs+　sorption　on　titanium　hexacyanoferrate　(Ti-Fe　PBA)　focusing　on　the　influence　of　the　structure　and　vacancies.　Ti-Fe　PBA　was　synthesized　with　specific　vacancies　using　a　coprecipitation　synthesis　method.　The　study　successfully　demonstrated　the　unique　structure　of　Ti-Fe　PBA　and　determined　the　ratio　of　vacancies　within　its　framework　through　various　characterization　techniques,　including　X-ray　diffraction,　Fourier　transform-infrared　spectrometry,　thermogravimetry,　scanning　elec-tron　microscopy,　X-ray　photoelectron　spectroscopy　and　sodium　hydroxide　titration.　The　synthesized　Ti-Fe　PBA　exhibited　an　impressive　Cs+　sorption　capacity　of　3.53　mmol　g+1　and　demonstrated　high　selectivity,　with　a　Kd　value　1.5　x　106　for　Cs+　sorption.　In　addition,　Ti-Fe　PBA　displayed　excellent　stability,　rapid　uptake　kinetics　and　maintained　high　selectivity,　even　in　the　presence　of　high　concentrations　of　coexisting　ions.　Moreover,　our　new　findings　revealed　that　K-Cs　ion　exchange　specifically　occurring　at　the　interstitial　sites　within　the　framework　structure　accounted　for-35　%　of　the　total　Cs+　sorption.　A　sorption-surface　complexation　model　utilizing　a　coupling　technique　that　integrated　PHREEQC　with　Python　enabled　in-depth　analysis　of　titration,　pH　effects　and　sorption　isotherms.　The　modelling　results　revealed　that　the　strong　ion　exchange　sites　=　SsOH　and　=　SsONa　on　surfaces　and　vacancies　contributed-65　%　of　the　total　Cs+　sorption.