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

The practical application of selective catalytic reduction with ammonia (NH₃-SCR) for NO_x 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.%) MnFeO_x 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% NO_x 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 NO_x emission control catalysts applicable to industrially relevant multi-poisoning conditions.