Macro-constructing zeolitic imidazole frameworks functionalized sponge for enhanced removal of heavy metals: The significance of morphology and structure modulation.

Rational synthesis of metal-organic frameworks (MOFs) via structural and morphology engineering are fundamental for enhanced heavy metal removal. Beyond tuning intrinsic characteristics, it is essential to address inseparability and instability issues of MOFs to fulfill the practical applications. Herein, we successfully constructed macroscopic zeolitic imidazole frameworks-functionalized melamine sponge (MS@ZIF, x represents the ultrasonication duration) using a facile dip-coating method. By varying ultrasonication duration, the morphology and structure of the loaded ZIF were modulated from leaf-shaped phase to hollow mixed phase to achieve the excellent adsorption performance. The optimized MS-ZIF exhibited significantly enhanced performance for Pb(II) and Cu(II) adsorption. Specifically, the MS-ZIF combined high adsorption capacities (624.8 and 588.6 mg g for Pb(II) and Cu(II), respectively), rapid kinetics, excellent anti-interfering capability (e.g., cations, dissolved organic matters) with outstanding reusability (removal efficiency > 91.8 % after 10 cycles). The MS-ZIF presented satisfactory performance on Pb(II) and Cu(II) removal in various real water matrices. Fixed-bed experiments were performed to assess the practicality of MS-ZIF, and 1821 bed volumes (BVs) and 1630 BVs of feeding streams containing Pb(II) and Cu(II) were effectively treated. This work proposed a novel paradigm for promoting the MOF's performance and simultaneously boosting MOF's application in actual heavy metal removal.