Fast and efficient adsorption of palladium from aqueous solution by magnetic metal-organic framework nanocomposite modified with poly(propylene imine) dendrimer

High-efficient removal of anionic dye from aqueous solution using metal-organic frameworks@chitosan aerogel rich in benzene structure

With the exponentially increase of dye pollutants, the purification of dye wastewater has been an urgent ecological problem. As a novel type of porous adsorbent, metal-organic frameworks still face challenges in recyclability, agglomeration, and environmentally unfriendly synthesis. Herein, MOF-525 was in-situ growth onto the surface of the chitosan (CS) beads to fabricate MOF-525@CS aerogel. CS was utilized as substrate to uniformly disperse MOF-525, thereby significantly mitigating agglomeration and improving recyclability of MOF-525. The characterization results shown that MOF-525@CS aerogel had a high specific surface area of 103.0 m2·g-1, and MOF-525 was uniformly distributed in the 3D porous structure of CS, and the presence of benzoic acid was detected. The MOF-525@CS aerogel had a remarkable adsorption capacity of 1947 mg·g-1 for Congo red, which is greater than the sum of its parts. MOF-525@CS aerogel also inherited the rapid adsorption ability of MOF-525, removing 80 % of Congo red within 600 min. Such excellent adsorption performance can be attributed to the benzoic acid trapped by CS via CN band to enhance the π-π stacking interactions. Additionally, the utilization of benzoic acid makes the synthesis process of MOF-525@CS aerogel more environmentally friendly. The high-efficient MOF-525@CS aerogel is a competitive candidate for dye pollution adsorption.

Highly porous organoclay-supported bimetal-organic framework (CoNi-MOF/OC) composite with efficient and selective adsorption of organic dyes

Herein, a highly porous bimetal-organic framework (bi-MOF) based on cobalt and nickel was successfully in situ grown on organoclay (OC) clusters by solvothermal method. Accordingly, the hierarchical porous CoNi-MOF/OC composite with a superior specific surface area of 2046 m²/g and a large pore volume of 0.763 cm³/g was obtained, which facilitated the adsorption of organic dyes. A morphological study using scanning electron microscopy indicated the formation of uniform bi-MOF crystals on the OC plates. Furthermore, the single- and multi-dye adsorption assays were implemented to precisely evaluate the adsorption capacity and selectivity of CoNi-MOF/OC composite to anionic and cationic dyes. The results revealed a high adsorption capacity of 58.61 mg/g at an adsorbent content of 15 mg, initial dye concentration of 20 ppm, and contact time of 25 min for MB, which is superior to several existing clay-based adsorbents. The adsorption kinetics study showed that the adsorption of cationic and anionic dyes onto the CoNi-MOF/OC composite followed the pseudo-second-order kinetic model. Interestingly, the regeneration study showed appropriate reusability and stability of the CoNi-MOF/OC composite for the removal of organic dyes with an almost unchanged structure after four regeneration cycles. The results of this study provide new insights for the rational design and fabrication of next-generation clay-based adsorbent by combining the synergistic advantages of bi-MOF with superior specific surface area and pore volume with organoclay composition and structure.