<p>Three FeOOH polymorphs (α-, β-, γ-) were synthesized and evaluated for n-butylamine carbonylation with CO₂. α-FeOOH exhibited relatively high catalytic performance (83.5% conversion, 99.7% selectivity at 160 ℃ under 5.0&#xa0;MPa) with excellent recyclability. The comprehensive characterization, such as XRD, BET, XPS, EPR, and TG-DSC/ESC, reveals that the catalytic activity is strongly correlated with two key factors: (1) surface hydroxyl concentration and (2) oxygen vacancy density, which are coupled with a balanced Bronsted-Lewis acid-base pair distribution. The superior performance of the α-phase stems from the synergistic effects of its oxygen-deficient surface (which enhances CO₂ activation) and the optimal distribution of acid-base sites (which stabilizes intermediates). This study establishes FeOOH polymorphs as potentially efficient catalysts for C-N coupling reactions and demonstrates that polymorph engineering is an effective strategy for CO₂ utilization.</p> Graphical Abstract