Rapid magnetic solid‐phase extraction of Congo Red and Basic Red 2 from aqueous solution by ZIF‐8@CoFe₂O₄ hybrid composites

Abstract

Core-shell metal-organic framework materials have attracted considerable attention mainly due to their enhanced or new physicochemical properties compared with their single-component counterparts. In this work, a core-shell heterostructure of CoFe2 O4 -Zeolitic Imidazolate Framework-8 (ZIF-8@CoFe2 O4 ) is successfully fabricated and used as an solid-phase extraction adsorbent to efficiently extract Congo Red and Basic Red 2 dyes from contaminated aqueous solution. Vibrating sample magnetometry indicates that the saturated magnetization of ZIF-8@CoFe2 O4 is 3.3 emu/g, which is large enough for magnetic separation. The obtained hybrid magnetic metal-organic framework based material ZIF-8@CoFe2 O4 can remove the investigated dyes very fast within 1 min of the contact time. The adsorbent ZIF-8@CoFe2 O4 also shows a good reusability. After regeneration, the adsorbent can still exhibit high removal efficiency (∼97%) toward Congo Red for five cycles of desorption-adsorption. This work reveals the great potential of core-shell ZIF-8@CoFe2 O4 sorbents for the fast separation and preconcentration of organic pollutants in aqueous solution before high-performance liquid chromatography analysis.

Metal–Organic Framework@Carbon Hybrid Magnetic Material as an Efficient Adsorbent for Pollutant Extraction

“…A high correlation coefficient was obtained by fitting the experimental adsorption equilibrium data using the Langmuir model (Figure S9), indicating that this model was suitable for describing the Congo red adsorption on ZIF-67@C-MOF-74. The maximum adsorption capacity of Congo red of the ZIF-67@C-MOF-74 was about 180 mg g –1 , which ranks among the highest ones reported in the literature using magnetic adsorbents − and was significantly higher than that of the carbon C-MOF-74 (Figure S10), demonstrating that the growth of ZIF-67 on the carbon, because of its reported excellent affinity to organic dyes, , improves the adsorbent properties of the material. It should be pointed out that, although Co-MOF-74 and ZIF-67 MOFs also exhibit high extraction capacity, the magnetic properties and the mesoporosity of the developed ZIF-67@C-MOF-74 hybrid material significantly improve the extraction process by allowing the easy recovery of the adsorbent and the access of larger organic molecules to its pore system, thereby facilitating the adsorbate–adsorbent interaction and enhancing the extraction performance.…”

Magnetic metal–organic framework composites: structurally advanced catalytic materials for organic transformations

“…In the final step, folic acid and IRMOF-3 were integrated by mixing zinc nitrate, NH 2 -H 2 BDC (or NH 2 -BDC) in DMF ethanol solution containing PVP, folic acid and OCMC coated Fe 3 O 4 NPs and finally heated in an autoclave at 100 o C for 6 h. Zhang along with research group prepared core-shell MOF composite for the solid phase extraction of Congo Red and Basic Red 2 dyes, wherein cobalt ferrite NPs were enclosed within zeolitic imidazolate framework (ZIF)-8 shells. 136 However, prior to covering with the MOF shell, cobalt ferrite NPs were initially coated with a layer of PVP polymer and then dispersed in the methanolic solution of zinc nitrate and 2methylimidazole with further refluxing at 70 o C for 20 h to form the ZIF-8@CoFe 2 O 4 core-shell magnetic composite (wherein CoFe 2 O 4 acted as the core component and ZIF-8 behaved like a shell). Wang and co-workers demonstrated the fabrication of a magnetic Fe 3 O 4 /Fe-MIL-101 composite via two-step encapsulation process.…”

Zeolitic imidazolate frameworks in analytical sample preparation

“…The organic ligand 2‐methylimidazole was immobilized on the polyvinylpyrrolidone coating the CoFe 2 O 4 nanoparticles followed by the addition of a Zn(II) solution to enable the in situ growth of a ZIF‐8 coating. The potential of the resulting ZIF‐8@CoFe 2 O 4 sorbent was applied to the MSPE of the dyes Congo Red and Basic Red 2 [43].…”