Electrochemical treatment systems have the unique ability to completely mineralize poly-and perfluoroalkyl substances (PFASs) through potential-driven electron transfer reactions. In this review, we discuss the state-of-the-art on electrooxidation of PFASs in water, aiming at elucidating the impact of different operational and design parameters, as well as reported mechanisms of PFAS degradation at the anode surface. We have identified several shortcomings of the existing studies that are largely limited to smallscale laboratory batch systems and unrealistic synthetic solutions, which makes extrapolation of the obtained data to real-world applications difficult. PFASs are surfactant molecules, which display significant concentrationdependence on adsorption, electrosorption, and dissociation. Electrooxidation experiments conducted with high initial PFAS concentration and/or in high conductivity supporting electrolytes likely overestimate process performance. In addition, the formation of organohalogen byproducts, chlorate and perchlorate, was seldom considered. Nevertheless, the first step toward advancing from laboratory-scale to industrial-scale applications is recognizing both the strengths and limitations of electrochemical water treatment systems. More comprehensive and rigorous evaluation of novel electrode materials, application of scalable proof-of-concept studies, and acknowledgment of all treatment outputs (not just the positive ones) are imperative. The presence of PFASs in drinking water and in the environment is an urgent global public health issue. Developments made in material science and application of novel threedimensional, porous electrode materials and nanostructured coatings are forging a path toward more sustainable water treatment technologies and potential chemical-free treatment of PFAS-contaminated water.

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The mechanism of photochemical CO2 reduction to formate by PCN-136, a Zr-based metal-organic framework (MOF) that incorporates light-harvesting nanographene ligands, has been investigated using steady-state and time-resolved spectroscopy and density functional theory (DFT) calculations. The catalysis was found to proceed via a “photoreactive capture” mecha-nism, where Zr-based nodes serve to capture CO2 in the form of Zr-bicarbonates, while the nanographene ligands have a dual role to absorb light and to store one-electron equivalents needed for catalysis. We also find that the process occurs via a “two-for-one” route, where a single photon initiates a cascade of electron/hydrogen atom transfers from the sacrificial donor to the CO2-bound MOF. The mechanistic findings obtained here illustrate several advantages of MOF-based architectures in the molecular photocatalyst engineering and provide insights on ways to achieve high formate selectivity.

Metrics & MoreArticle Recommendations * sı Supporting Information S everal errors in the cited rate constant values were recently discovered in our original review article (10.1021/acs.est. 0c06212), as listed below, and in the Supporting Information. The corrected values do not affect the discussion or conclusion of our paper.Page 14817, left column, line 42: "100 mM K 2 HPO 4 (k = 1.3 × 10 −4 m s −1 )" should read "100 mM Na 2 SO 4 (k = 8.81 × 10 −6 m s −1 )".Page 14817, left column, line 43: "20 mM NaClO 4 (k = 8.81 × 10 −6 m s −1 )" should read "20 mM NaClO 4 (k = 4.3 × 10 −6 m s −1 )".Page 14823, left column, line 45: "(4.4 × 10 −5 m s −1 )" should read "(1.3 × 10 −4 m s −1 )".Page 14823, left column, line 45: "(1.3 × 10 −4 m s −1 )" should read "(4.4 × 10 −5 m s −1 )".Page 14823, right column, line 8: "(9.33 × 10 −5 m s −1 ) and BDD (1.09 × 10 −5 m s −1 )" should read "(1.92 × 10 −5 m s −1 ) and BDD (2.80 × 10 −5 m s −1 )".Page 14823, right column, line 36: "6.13−9.33 × 10 −5 m s −1 " should read "0.567−2.43 × 10 −5 m s −1 ". ■ ASSOCIATED CONTENT * sı Supporting InformationThe Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.2c08354.Description of quantum mechanical simulations, electric energy per order calculations, and a summary of state-ofthe-art on electrochemical oxidation of PFASs (PDF)