Hydrogen gas adsorption capacity of halloysite nanotubes loaded with metal-organic frameworks

Abstract

Halloysite is a natural, eco-friendly, material abundant that has different charges inside and outside of its structural tubular nanoparticles. The adsorption performance of the material was improved by modifying halloysite nanotubes (HNTs) to prepare a nanocomposite. Metal-organic frameworks (MOF: HKUST-1) as gas adsorbents were loaded inside the halloysite to produce the composite. An etching process using sulfuric acid was performed to increase the loading efficiency by expanding the inner space of the halloysite to effectively load precursor solution; the resulting material was known as etched HNTs (EHNTs). Structural analysis was performed with X-ray diffraction (XRD), and morphological analysis was conducted using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In addition, the hydrogen and nitrogen adsorption capacities were measured using Brunauer-Emmett-Teller (BET) equipment. The results confirmed improved adsorption capacity of both N2 and H2 by HKUST-1@EHNT(5M) compared to that of HKUST-1@EHNT(1M). Etching at high concentrations allowed a larger inner space and load amount of HKUST-1. This study presented the possibility of synthesizing various hybrid materials using nanotubes, and we expect that the halloysite nanocomposite synthesis process can be used in gas adsorption applications.