Physisorption-chemisorption coupling mechanism in the 1D–2D network stacking of carbon-based materials with COOH-surface functionalization

Abstract Carbon allotropes are remarkable materials with diverse applications, including aquatic pollutant degradation via physisorption and/or chemisorption mechanisms. Different forms of carbon allotropes exhibit different adsorption mechanisms, which make them suitable as a role model to develop highly efficient adsorbents. Here, we manipulate the adsorption mechanism of multiwall carbon nanotube (MWCNT), which is known to possess dominant physisorption through COOH-functionalization to enable its chemisorption for effective use in water treatment applications. We expect that the –COOH functionalization could play a significant role in enhancing hydrogen bonding and π–π interaction while also improving nanocomposite dispersibility, which further increases dye adsorption capacity. Moreover, by connecting the –COOH roots on the MWCNT surface with graphene, which is also known to have a good physisorption, a one-dimensional-two-dimensional (1D–2D) stacking structure was formed and constructed a three-dimensional (3D) network nanocomposite accordingly. In this model, we found that the –COOH not only provokes a chemisorption, but also serves as a bridge to promote a well-ordered structured 1D–2D stacking, optimizing surface energy both MWCNT and graphene, and further improving methylene blue dye degradation via strong physisorption. Among the tested samples, graphene/MWCNT-COOH nanocomposite with 60% graphene demonstrated the highest dye adsorption ability, achieving 98.02% adsorption efficiency and 82.87 mg g −1 adsorption capacity uptakes surpassing the control sample without –COOH functionalization and their pristine states. The findings from this study provide insights into the surface modification strategies for advanced carbon-based adsorption materials and open up the potential of –COOH-functionalized carbon nanomaterials for efficient water pollutant degradation.