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We systematically investigated the conditions that lead to the loss of swelling ability, using protonic layered perovskite crystals of HCa2Nb3O10·1.5H2O as a representative example. The crystals were stored under various conditions, including ambient air, sealed environments, and dry/humid conditions, both in the dark and under light. Their reactivity with dimethylaminoethanol (DMAE) was then examined. We found that only the crystals exposed to ambient air for more than 10 days lost their swelling ability, whereas those stored under other conditions retained their reactivity. Based on these results, we speculated that ammonia, the most abundant alkaline component in the atmosphere, is absorbed from the air via acid-base interaction. This hypothesis was confirmed through XRD and FT-IR characterization. We conclude that trace amounts of ammonia in the atmosphere intercalate into the acidic interlayer galleries and are responsible for the degradation in reactivity. Furthermore, the original reactivity can be easily restored by acid treatment, which replaces the intercalated ammonium ions with protons, thereby recovering the swelling capability.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: layered metal oxide, swelling reactivity

Date published: 2025-09-16

Publisher: American Chemical Society (ACS)

Journal:

• Langmuir (ISSN: 07437463) vol. 41 issue. 36 acs.langmuir.5c03503

Funding:

• Ministry of Education, Culture, Sports, Science and Technology
• Core Research for Evolutional Science and Technology JPMJCR22B1

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1021/acs.langmuir.5c03503

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Updated at: 2025-09-17 12:30:20 +0900

Published on MDR: 2025-09-17 12:18:27 +0900