Thermocatalytic　or　photocatalytic　CO2reduction　to　CO─without　H2or　sacrificial　hole　scavengers─remains　challenging　due　to　prohibitively　high　energy　barriers　or　the　lack　of　coupled　oxidation　half-reactions.　Photothermal　catalysis　enables　autonomous　CO2dissociation　via　synergistic　photon-thermal　activation　under　mild　conditions.　However,　it　remains　a　grand　challenge　to　design　high-performance　catalysts　that　achieve　rapid　lattice　oxygen　dynamic　equilibrium　by　harmonizing　photogenerated　carriers　with　thermal　lattice　vibrations.　Here,　we　report　K-doped　Nb2O5nanoribbons　(K–Nb2O5NRs)　that　synergistically　integrate　photothermal　energy　and　lattice　oxygen　redox　cycling　to　effect　direct　CO2decomposition　under　mild　photothermal　conditions　(50–250　°C).　The　K–Nb2O5NRs　achieve　CO　production　rates　of　4.1–405　μmol·g–1·h–1with　100%　selectivity,　outperforming　undoped　Nb2O5by　6.3-fold　at　250　°C.　Mechanistic　studies　reveal　that　K　doping　optimizes　the　electronic　structure　of　Nb2O5,　accelerating　oxygen　vacancy　regeneration　and　enhancing　CO2adsorption.　At　the　same　time,　the　photothermal　effect　decouples　lattice　oxygen　oxidation　(photogenerated　holes)　and　CO2reduction　(photogenerated　electrons),　thereby　suppressing　electron–hole　recombination.　By　introducing　H2O　as　a　dynamic　oxygen　chemical　potential　modulator,　the　H2/CO　ratio　is　continuously　tuned　from　1.4　to　0.3　through　competitive　adsorption　at　oxygen　vacancy　sites.　Remarkably,　the　catalyst　maintains　syngas　production　for　50　h　in　a　flow　reactor.　This　study　provides　new　ideas　for　the　design　of　catalysts　for　photothermal　CO2conversion.　©　2025　American　Chemical　Society