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ABSTRACT Recovering palladium (Pd) from low‐concentration metallurgical wastewater still poses significant challenges. In this study, triaminoguanidine hydrochloride was used as the key functional site, and three guanidine‐functionalized covalent organic frameworks (GCOFs) were successfully constructed by adjusting the substituents (–H, –OH, and –OCH 3 ) on terephthalaldehyde molecules, and their extraction performance towards palladium was explored. First, multiple characterization techniques, including scanning electron microscopy, zeta potential analysis, and contact angle measurement, were employed to systematically investigate the regulatory rules of substituents on the physicochemical properties of GCOFs, such as their micromorphology, surface potential, and hydrophilicity. Second, static adsorption experiments were conducted to systematically study the adsorption behavior of GCOFs with different substituents toward Pd(II), and the maximum sorption capacity of COF‐H is up to 180 mg g −1 . Furthermore, this study successfully fabricated GCOFs into aerogels by means of freeze‐drying technology and conducted dynamic adsorption experiments with actual metallurgical wastewater. Specifically, 70.0 mg of COF‐H/aerogel is capable of continuously treating 12.5 L of metallurgical wastewater. In conclusion, by regulating the types of substituents, this study clarified the influence rules of substituent effects on the Pd(II) adsorption performance of GCOFs in metallurgical wastewater. The developed GCOFs/aerogels hold broad application potential in the fields of precious metal resource recovery and environmental protection.
Xiong et al. (Fri,) studied this question.