Fe3O4@calcium　silicate　hydrate　(CSH)　nanosheets　composite　adsorbents　were　obtained　through　electrostatic　interaction.　And　an　＇adsorbent-to-photocatalyst＇　transformation　strategy　was　proposed:　the　harmful　heavy　metal　ions　from　the　polluted　water　were　removed　by　Fe3O4@CSH　adsorbents,　after　which　they　were　recycled　and　reused　as　photocatalysts　for　CO2　reduction.　The　results　demonstrated　that:　benefiting　from　ultrahigh　surface　area　and　strong　ion　exchange　ability　of　CSH　nanosheets,　heavy　metal　ions　including　Zn2+,　Cu2+,　Co2+,　Ni2+,　and　Pb2+　could　be　efficiently　removed　by　Fe3O4@CSH　adsorbents.　The　maximal　adsorption　capacities　were　83,　142,　150,　179,　343　mg/g,　respectively.　Fe3O4@CSH　adsorbents　containing　heavy　metal　ions　could　efficiently　reduce　CO2　to　CO　under　visible　light.　Particularly,　Fe3O4@CSH-Ni　after　adsorption　of　Ni2+　showed　the　best　catalytic　activity.　The　CO　generation　rate　was　up　to　3　310　μmol/(gh)　with　a　high　selectivity　of　99.3%.　Besides,　the　magnetic　property　of　Fe3O4　enabled　the　rapid　recovery　of　Fe3O4@CSH　during　the　adsorption　and　photocatalysis　processes.　©　2021,　Editorial　Department　of　Journal　of　the　Chinese　Ceramic　Society.　All　right　reserved.