Pyrene‐Based Covalent Organic Frameworks With Diacetylene Linkers for Tandem Adsorption and Photodegradation of Perfluorooctanoic Acid

Abstract

Per‐ and polyfluoroalkyl substances (PFAS) are anthropogenic water contaminants that pose severe risks to human health and the environment, and strategies for PFAS remediation are urgently needed. Here, we present a combined experimental and computational study of a tetragonal Py‐DEBD framework, as both an adsorbent and a heterogeneous photocatalyst for the degradation of PFOA. Through batch photodegradation experiments, we found that Py‐DEBD adsorbed and degraded PFOA, and as the solution pH decreased from 4 to 2, PFOA adsorption capacity and degradation rate increased. For photocatalytic degradation experiments at a pH of 2, over 99% of PFOA was removed from the solution, and 32% defluorination was achieved within 24 h. The solution concentrations of short‐chain degradation byproducts initially increased during photodegradation, and several peaked and then decreased with continued irradiation as they were photochemically degraded. Density functional theory simulations demonstrate favorable adsorption of PFOA onto the Py‐DEBD and show that photoinduced charge transfer under UV irradiation leads to PFOA oxidation, supporting the decarboxylation‐hydroxylation‐elimination‐hydrolysis (DHEH) mechanism for PFOA photo‐oxidative degradation. This work, therefore, uncovers a fundamental strategy for designing metal‐free porous materials for adsorption and photocatalytic degradation and opens a promising avenue for the development of photoactive adsorbent materials for contaminant remediation.