Uptake of indoor VOC BTEX on pillared montmorillonites with emphasis on pore structure and surface chemistry

Indoor exposure to volatile organic compounds (VOCs), especially BTEX (benzene, toluene, ethylbenzene, xylene), poses serious health risks due to their toxicity and persistence. In this study, we synthesized three pillared interlayered clays (PILCs) Al-, Zr-, and Ti-PILC by intercalating polyoxocations into Na-montmorillonite (Na-MMT) and evaluated their efficacy for BTEX adsorption. Structural characterization revealed significant enhancement in surface area (Na-MMT: 65 m 2 ·g −1 ; Al/Zr-PILC: 150–158 m 2 ·g −1 ) and microporosity ( V µ ≈ 0.029 cm 3 ·g −1 ) in Al- and Zr-pillared samples. The adsorption isotherms at 25°C followed a dual-site Langmuir–Freundlich (DSLF) model (R 2 ≥ 0.986), capturing both monolayer and multilayer interactions. Zr-PILC demonstrated the highest benzene and xylene uptakes (1.025 and 0.495 mmol·g −1 ), attributed to Lewis-acid Zr 4+ centers and a broad mesopore distribution. Al-PILC showed superior toluene and ethylbenzene adsorption (0.720 and 0.384 mmol·g −1 ), linked to Brønsted-acid OH groups and balanced micro–mesoporosity. Ti-PILC offered uniform adsorption across VOCs due to high external surface area (108 m 2 ·g −1 ), albeit with limited micropore volume. Adsorption potential analysis further validated that molecular descriptors like kinetic diameter, polarizability, dipole moment and VOCs architecture jointly determine its uptake. The thermodynamic profiles and affinity trends suggest that PILCs can be rationally tuned to achieve selective, regenerable adsorption of indoor VOCs. This work provides the first comparative assessment of Zr-, Al-, and Ti-PILCs for BTEX capture, highlighting their potential as robust alternatives to activated carbon in air purification systems. • Zr-, Al-, and Ti-pillared montmorillonites were synthesized and evaluated for BTEX adsorption. • Zr-PILC showed the highest benzene (1.025 mmol·g −1 ) and xylene (0.495 mmol·g −1 ) uptake. • Al-PILC exhibited optimal balance for toluene and ethylbenzene due to its micropore–mesopore synergy. • The Dual-Site Langmuir–Freundlich model captured the dual-phase adsorption mechanism with R 2 ≥ 0.986. • Adsorption correlated with VOC properties (kinetic diameter, polarizability, etc .) enabling rational sorbent design.