Adsorption Properties of Hydrated Cr³⁺ Ions on Schiff-base Covalent Organic Frameworks: A DFT Study

Considering the superior physiochemical property, increasing efforts have been devoted to exploiting the covalent organic frameworks (COFs) materials on the environmental remediation of heavy metal ions. Water pollution caused by Cr³⁺ metal ions is of special concern for scientists and engineers. Notwithstanding all the former efforts made, it is surprising that very little is known about the interaction mechanisms between the hydrated Cr³⁺ metal ions and COF materials. In present context, density functional theory (DFT) method is used to elucidate geometric and electronic properties with the purpose of putting into theoretical perspective the application values and interaction mechanisms for COF materials on Cr³⁺ capture. The results showed that all the five selected Schiff-base COFs materials displayed good adsorption performance on Cr³⁺ removal while the phenazine-linked and imine-COFs possessed the most favorable adsorption capacity due to the optimal chemical units and frameworks. The hydration effect was found to play a two-side role in the adsorption process and interaction mechanisms, involving coordination, hydrogen bonds, as well as weak non-covalent interactions, have been illuminated to explain the observed different adsorption behaviors. This study provides a general guidance for the design and selection of efficient COF materials as high-capacity Cr³⁺ adsorbents.