Two-dimensional　(2D)　SAPO-5　nanosheets　with　a　thickness　of　about　3.0nm　were　fabricated　successfully　by　a　facile　one-pot　hydrothermal　method　for　the　first　time.　The　structure　and　the　physicochemical　properties　of　the　as-prepared　SAPO-5　nanosheets　were　characterized　in　detail.　The　SAPO-5　ultrathin　nanosheets　have　great　potential　applications　for　the　highly　efficient　reduction　of　CO2　into　a　renewable　hydrocarbon　fuel.　Compared　with　SAPO-5　microrods,　the　ultrathin　SAPO-5　nanosheets　show　higher　photocatalytic　activity　(about　6　times)　for　reducing　CO2　into　CH4.　It　is　found　that　a　large　number　of　surface　active　sites　on　the　nanosheets　make　it　suitable　for　the　catalytic　reaction,　and　the　ultrathin　geometry　of　the　nanosheets　promotes　the　mass　transfer　of　reactants　and　products.　The　normalized　time-resolved　fluorescence　decay　signals　of　the　photo-induced　absorption　recorded　from　the　SAPO-5　nanosheets　and　rod　indicate　that　the　excited　state　can　survive　longer　on　the　nanosheets,　which　also　contributes　to　its　high　photocatalytic　activity.　Meanwhile,　high　CO2　adsorption　capacity　may　be　one　important　reason　for　high　photocatalytic　activity　of　SAPO-5　nanosheets.　The　reaction　intermediates　are　detected　by　in-situ　FT-IR　spectroscopy.　Finally,　a　probable　mechanism　is　proposed　based　on　the　experimental　results.　It　is　hoped　that　our　work　could　facilitate　the　fabrication　of　molecular　sieve　materials　for　solar　energy　conversion　of　CO2.　©　2016　Elsevier　B.V.