Stabilization of bare divalent Fe(II) cations in Al-rich beta zeolites for superior NO adsorption

• NO was concentrated on Fe(II) in zeolites even in the coexistence of excess oxygen.
• Al-rich beta zeolite enabled Fe(II) to hold NO as much as NO/Fe(II) molar ratio of 2.
• Al distribution in zeolite is a key to hold ions in a coordinately unsaturated state.

Fe(II)-beta zeolites with a Si/Al molar ratio of 5, synthesized in the absence of an organic structure-directing agent, showed remarkably efficient NO chemisorption, as compared to conventional Si-rich beta zeolites (Si/Al = 12–20) and common zeolites such as A-type zeolite, ZSM-5, and faujasite.

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