Poly(sodium 4-styrenesulfonate) brushes-functionalized UiO-66-NH2 metal-organic framework for high and selective adsorption of dyes

Advanced adsorbents with high adsorption capacity and adsorption selectivity are desirable. Here, a Zr-based metal-organic framework (MOF), UiO-66-NH2 @poly(sodium 4-styrenesulfonate, Nass), was synthesized using the high surface area of MOFs as a substrate and the high grafting density of surface initiated-atom transfer radical polymerization (SI-ATRP). UiO-66-NH2 @poly(Nass) was used to adsorb different dyes. The maximum adsorption capacity (Qm) of methylene blue (MB) and basic fuchsine (BF) was 299.8 and 789.2 mg·g−1, respectively, which were higher than those of Sudan I (SD I, 6.340 mg·g−1), neutral red (NR, 188.1 mg·g−1), methyl orange (MO, 199.5 mg·g−1), and acid chrome blue K (AK, 122.3 mg·g−1). The adsorption isotherms and kinetics were investigated, and it was confirmed that the Langmuir isotherm and the pseudosecond-order kinetic model fit our adsorbents. In the binary mixed solution, the removal rate (R) of MB reached 64.44%, while that of MO was only 3.340% for MB/MO. R was 64.29% for MB and 21.97% for AK for MB/AK and 97.45% for BF and 30.03% for MO for BF/MO, verifying the preferential selectivity to adsorb basic dyes. The superior adsorption was ascribed to multiple interactions, including electrostatic interaction, hydrogen bonding, and π–π accumulation. In addition, the effect of grafting poly(Nass) on the pore size of UiO-66-NH2 was studied. The excellent stability showed that the R dropped by less than 15.62% after five consecutive cycles. The UiO-66-NH2 @poly(Nass) was applied in the determination of MB and BF in water, crucian carp, and green shrimp. Good linearity was observed for MB (R2 = 0.9971) and BF (R2 = 0.9993) in the range of 0.2–30 and 0.5–50 μg·mL-1, respectively, with satisfactory recoveries (in the range of 87.45–101.3% for MB and 90.34–98.86% for BF), achieving favorable practicability.