To　understand　at　a　molecular　level　the　nature　of　iron-catalyzed　selective　reduction　of　NO　by　hydrocarbons　(HC-SCR),　binuclear　it-hydroxo-bridged　iron　clusters　with　a　well-defined　structure　were　constructed　in　cavities　of　Y　zeolite　by　surface　organometallic　chemistry　of　ferrocene　and　were　characterized　by　extended　X-ray　absorption　fine　structure　spectroscopy　and　NO　adsorption　monitored　by　infrared　(IR)　spectroscopy.　IR　spectroscopy　was　used　to　study　in　detail　the　SCR　of　NO　by　propylene,　ethylene,　and　methane　over　these　well-defined　iron　sites.　The　results　reveal　that　the　NO　reduction　undergoes　different　reaction　pathways,　depending　on　the　type　of　hydrocarbon　reductants　and　the　reaction　temperature.　In　the　absence　of　O-2,　propylene　can　reduce　NO　coadsorbed　over　Fe　sites　by　a　NO　adduct　mechanism　at　room　temperature,　while　at　high　reaction　temperatures　greater　than　150　degrees　C,　NO2　produced　by　the　disproportionation　reaction　of　NO　contributes　in　major　part　to　the　SCR　reaction.　NH3　produced　by　the　sequential　reactions　of　olefins,　acetaldehyde,　acetic　acid,　and　nitro-compounds　with　NO2　was　found　to　be　a　key　intermediate　for　the　formation　of　N-2.　The　nitro-compounds　formed　by　coadsorption　of　reductant　and　oxidant　over　Fe　sites　may　be　the　key　intermediates　initiating　the　reduction　process　at　high　temperature.　Methane　as　a　reductant　represents　a　NO2　reduction　pathway　different　from　propylene　and　ethylene.　It　is　oxidized　to　CO2,　CO,　and　H2O　probably　via　the　nitromethane　pathway,　while　NO2　is　directly　reduced　to　N-2.　The　whole　reaction　network　of　the　iron-catalyzed　HC-SCR　in　the　absence　of　O-2　was　proposed　and　discussed　by　a　combination　of　literature　with　some　important　intermediates　observed　such　as　R-CN,　HNCO,　-COO-,　and　NH3.　The　catalytic　results　show　that　the　presence　of　O-2　greatly　aids　in　the　iron-catalyzed　reduction　of　NO　to　N-2,　but　the　intrinsic　reduction　pathway　is　not　changed.