Descriptor‐Led Nonmetal Doping of MnO ₂ Enables Selective NH ₃ ‐SCR With Suppressed N ₂ O Formation

Low‐temperature ammonia‐selective catalytic reduction (NH 3 ‐SCR) over MnO 2 is attractive for nitrogen oxides (NO x ) abatement yet is intrinsically penalized by nitrous oxide (N 2 O) formation, a potent greenhouse byproduct. Here, we show that oxygen‐site nonmetal substitution in β ‐MnO 2 can simultaneously suppress N 2 O and accelerate NH 3 ‐selective SCR, enabled by a feasibility‐to‐mechanism computational workflow. Screening by structural compatibility, orbital hybridization, thermochemical and kinetic stability identifies viable dopants, among which F and S most effectively rewire reaction branching. Kinetics estimated by the density functional theory calculations reveal that F and S raise the N 2 O‐forming rate‐determining barrier from 0.80 eV to 0.93/0.92 eV, while lowering the N 2 ‐forming barrier from 0.48 eV to 0.40/0.42 eV. At 200°C, F‐ and S‐doped β ‐MnO 2 increase TOF by a factor of 8.40 and 4.24, respectively, and enhance kinetic N 2 selectivity by a factor of 1.66 and 1.38, respectively. We identify Mn( d )–nonmetal( p ) band center alignment as a mechanistic descriptor that points to a volcano‐like trend for the energy barriers of N 2 O and N 2 , supported by Bader charge, COHP/ICOHP, and ELF analyses. These results serve as a theoretical design reference for tuning the activity–selectivity trade‐off in oxygen‐site–modified oxide SCR catalysts.