Yolk-shell zeolite nanoreactors enable multi-poison resistance for NOx reduction

The practical application of selective catalytic reduction with ammonia (NH3-SCR) for NOx abatement from stationary sources is severely restricted by catalyst deactivation induced by SO2 and alkali metal poisons in flue gas. Although integrating transition metal oxides with zeolites is widely pursued to enhance catalyst poisoning tolerance, most reported strategies have inherent limitations. Conventional loading approaches deliver high active phase loading but leave active sites directly exposed to poisons, whereas confinement strategies offer shielding protection but typically suffer from limited active phase content. Herein, we demonstrate the concept of a zeolite-confined nanoreactor by constructing a yolk-shell structured catalyst, in which high-content (> 10 wt.%) MnFeOx nanoparticles are encapsulated within a hollow ZSM-5 zeolite shell. In situ extended X-ray absorption fine structure spectroscopy (EXAFS) and diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS), combined with density functional theory (DFT) calculations, reveal a synergistic dual-shielding mechanism: the ZSM-5 zeolite shell physically hinders SO2 from accessing and poisoning the inner active oxides core, while its intrinsic framework Brønsted acid sites chemically suppress SO2 adsorption and trap alkali metal species. Consequently, the catalyst maintains over 95% NOx conversion at 250 °C under co-poisoning by SO2 and potassium. This work establishes hollow zeolite-confined nanoreactors as an effective and versatile platform for developing durable NOx emission control catalysts applicable to industrially relevant multi-poisoning conditions. Ammonia selective catalytic reduction for stationary NOx removal is limited by catalyst deactivation caused by SO2 and alkali metals in flue gas. Here, the authors develop a zeolite-confined yolk-shell nanoreactor that enables stable long-term operation under industrially relevant poisoning conditions.