High‐Capacity Adsorption and Thermal Destruction Adaptable to PFAS Chain Length via Crystal‐to‐Crystal Transformation of Zirconium–Organic Framework

Abstract

ABSTRACT Per‐ and polyfluoroalkyl substances (PFAS) face the most stringent drinking water quality standards ever due to their potential toxicity and bioaccumulation potential. Their removal from water is commonly accomplished by adsorption, which is generally ineffective for short‐chain PFAS and unreliable for other homologues with diverse physicochemical properties. Here, we present a versatile platform based on zirconium‐based metal–organic frameworks (MOFs) to remove PFAS with different chain lengths via crystal‐to‐crystal transformation. The MOF [Zr 6 (μ 3 ‐O) 4 (μ 3 ‐OH) 4 PTA 3 (H 2 O) 4 ] n ( Zr‐PTA1 , PTA = 4,4′,4″,4′″‐(4,4′‐(1,4‐phenylene) bis (pyridine‐6,4,2‐triyl))tetrabenzoic acid) exhibits exceptional adsorption capacity for C8 PFAS (2945 ± 173 mg/g for perfluorooctanoic acid (PFOA) and 2322 ± 28 mg/g for perfluorooctane sulfonate (PFOS)), while its crystal‐to‐crystal transformation product [Zr 6 (μ 3 ‐O) 4 (μ 3 ‐OH) 4 PTA 2 (CH 3 COO) 4 ] n ( Zr‐PTA2 ) with abundant open metal sites (OMS) targets shorter‐chain C4 PFAS (375 ± 9 mg/g for perfluorobutanoic acid and 414 ± 41 mg/g for perfluorobutanesulfonic acid), surpassing all previously reported MOFs. Flow‐through column tests demonstrate rapid PFAS removal below 4 ng/L. This exceptional performance is due to distinct structural motifs—steric host–guest fit of Zr‐PTA1 for long‐chain PFAS versus OMS‐driven chemisorption of short‐chain PFAS by Zr‐PTA2 . Importantly, the framework facilitates subsequent thermal‐catalytic PFAS destruction, achieving 97 ± 5% PFOA degradation efficiency with 79 ± 0.3% fluoride recovery.