Adsorption and Photocatalytic Activity of Covalent Organic Frameworks for Environmental Remediation: A Review of Density Functional Theory Studies

The contamination of water resources by heavy metals, radionuclides, and organic pollutants demands efficient materials for water treatment. Covalent organic frameworks (COFs) are promising candidates owing to their tunable porosity and functionalizable frameworks. This review examines density functional theory (DFT) studies of COFs for environmental remediation, distinguishing three frequently conflated processes: adsorptive capture, photocatalytic transformation, and combined adsorption–photocatalysis. Studies are analyzed across heavy metals, radionuclides, and organic pollutants, including antibiotics, pharmaceuticals, per- and polyfluoroalkyl substances (PFASs), dyes, pesticides, flame retardants, and others. Photocatalytic applications, including hydrogen peroxide (H2O2) production and others, are treated separately in terms of band alignment, charge separation, and reaction free energies. This review also assesses methodological limits of current DFT practice, including the incomparability of adsorption energies across functionals and model types, the distinction between adsorption energy and adsorption free energy, and the gap between computed energetics and experimental capacities.