The　alkali　metal　(M　=　Na,　K,　Rb,　and　Cs)-modified　C-FDU-15　(M-C-FDU-15(x);　x　was　the　M/C-FDU-15　M　ratio,　and　equal　to　0.01-0.03)　samples　were　prepared　through　an　in　situ　process,　and　characterized　by　means　of　the　TG,　XRD,　TEM,　EDS,　N-2　adsorption-desorption,　O-2-TPD,　and　CO2-TPD　techniques.　The　(NO　+　O-2)　adsorption　mechanism　was　investigated　using　the　(NO　+　O-2)-TPD　and　DRIFTS　techniques.　The　results　show　that　the　sequence　of　(NO　+　O-2)　adsorption　performance　was　Na-C-FDU-15(0.01)　(104.　1　mg/g)　＞　K-C-FDU-15(0.01)　(92.4　mg/g)　＞　C-FDU-15　(76.2　mg/g)　＞　Rb-C-FDU-15(0.01)　(65.1　mg/g)　＞　Cs-C-FDU-15(0.01)　(62.3　mg/g).　The　alkali　metal　was　uniformly　distributed　in　C-FDU-15　and　its　doping　enhanced　the　amount　of　the　basic　sites　in　the　sample.　Moreover,　the　optimal　Na/C-FDU-15　M　ratio　was　0.02.　(NO　+　O-2)　were　chemically　adsorbed　mainly　in　the　forms　of　nitrite　(NO2)　and　nitrate　(NO3)　on　M-C-FDU-15(x).　A　more　amount　of　NO　was　converted　to　nitrate　than　to　nitrite.　There　were　three　key　factors　of　enhancing　the　(NO　+　O-2)　adsorption　capacity　of　C-FDU-15　due　to　alkali　metal　doping:　the　first　factor　was　the　increasing　of　surface　area　and　pore　volume　of　the　sample,　the　second　one　was　the　enhancement　in　amount　of　the　active　sites　in　the　sample,　and　the　third　one　was　the　smaller　alkali　metal　ionic　radius　in　the　sample.　(C)　2020　Elsevier　Inc.　All　rights　reserved.