Postsynthetic Modification of Zeolite Internal Surface for Sustainable Capture of Volatile Organic Compounds under Humid Conditions

Kang Min Lee; Nam Sun Kim; Muhammad Numan; Jeong-Chul Kim; Hae Sung Cho; Kanghee Cho; Changbum Jo

doi:10.1021/acsami.1c16108

Postsynthetic Modification of Zeolite Internal Surface for Sustainable Capture of Volatile Organic Compounds under Humid Conditions

ACS Appl Mater Interfaces. 2021 Nov 17;13(45):53925-53934. doi: 10.1021/acsami.1c16108. Epub 2021 Nov 2.

Authors

Kang Min Lee¹, Nam Sun Kim¹, Muhammad Numan¹, Jeong-Chul Kim², Hae Sung Cho³, Kanghee Cho⁴, Changbum Jo¹

Affiliations

¹ Department of Chemistry and Chemical Engineering, Inha University, 100 Inha-ro, Michuhol-gu, Incheon 22212, Republic of Korea.
² Center for Nanomaterials and Chemical Reactions, Institute for Basic Science (IBS), Daejeon 34141, Republic of Korea.
³ School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China.
⁴ Climate Change Research Division, Korea Institute of Energy Research, 152 Gajeong-ro, Yuseong-gu, Daejeon 34129, Republic of Korea.

PMID: 34726376
DOI: 10.1021/acsami.1c16108

Abstract

Although low-cost, high-surface-area crystalline aluminosilicate zeolites have been recognized as promising adsorbents for the capture of volatile organic compounds (VOCs), their hydrophilic nature leads to a significant loss of performance owing to the ubiquitous presence of water vapor in the VOC stream. Herein, the aluminosilicate zeolites (i.e., mordenite and nanocrystalline β) are functionalized via a solvothermal post-treatment with methyl iodide as the grafting agent. The methyl groups are primarily attached to the zeolite internal surface via covalent bonding between internal bridging O and -CH₃, as evidenced by multiple analysis data. The static isotherms and diffusional studies clearly reveal a remarkable decrease in both the rate of water adsorption and the water affinity due to the attachment of methyl groups to the micropore walls, thus enhancing the water tolerance compared to that of pristine zeolites. In addition, CH₃I-functionalized zeolites are investigated as adsorbents for the removal of benzene under dry and humid conditions, and their performance is compared to that of CH₃Si(-OCH₃)₃-functionalized zeolites, wherein the methyl groups have been grafted onto the external surface. The results demonstrate that, although the benzene adsorption capacity under dry conditions is decreased upon internal surface functionalization, the loss of VOC adsorption capacity in the presence of H₂O vapor is effectively prevented. By contrast, external surface functionalization is ineffective for preventing the negative effects of moisture upon the benzene adsorption capacity. As a result, CH₃I-functionalized zeolites exhibit superior dynamic adsorption performance for benzene at 318 K under humid conditions (relative humidity: 80%), with a saturated adsorption capacity of 64.9 mg g^-1. This work provides an easy strategy for tailoring the adsorption properties of aluminosilicate zeolites for adsorption/separation and other advanced applications.

Keywords: adsorption; functionalization; humidity; volatile organic compounds; zeolites.