Regulating adsorption-desorption through controlled modification of the 2D pores in layered double hydroxides

Abstract

Selective transport and adsorption in two-dimensional (2D) materials depend on the affinity and molecular size of the adsorbate. However, until now studies have predominantly been restricted to small molecules (<1 nm), limiting their use in drug delivery, catalysis, and agriculture applications, which require the inclusion of larger molecules (∼1–3 nm). In this study, we utilize a simple methodology to modify the interlayer structure of layered doubled hydroxide (LDH). Using benzene sulfonate surfactants of increasing carbon tail length, we induce 2D pores ranging between 1.7–3 nm while maintaining a similar intergallery chemical environment. The synthesized composites were thoroughly characterized by XRD, FTIR, HRTEM, XPS, and ICP. Our findings reveal that the interlayer d-spacing is linearly correlated to the molecular size of the surfactant. Additionally, both the internal diffusion parameter of the Morris-Weber model (Kint), as well as the internal capacity of Methylene Blue (MB) were found to be linearly correlated to the interlayer d-spacing measured by XRD. Moreover, we found that the desorption trend of MB from the modified LDHs correlates with the chemical affinity to the modified LDH surface as well as the amounts of MB adsorbed internally and externally. Overall, the results highlight the potential of LDH-based materials to serve as a promising material platform with a controlled molecular adsorption capacity and diffusion rate.