To enhance the dye
adsorption capacity of zeolitic imidazolate
framework-67 (ZIF-67), phosphotungstic acid (HPW) was integrated into
ZIF-67 to prepare composite adsorbents. Characterization results demonstrated
that the electronegative HPW was uniformly and tightly deposited on
the electropositive ZIF-67. Methylene blue (MB) was selected as a
model contaminant to evaluate the adsorption performance of hybrid
adsorbents. Results showed that HPW@ZIF-67 had excellent adsorption
capacity toward cationic MB. The optimal ZIF-67-0.2 HPW sample with
a HPW dosage of 9.9 wt % presented an adsorption capacity of 446.4
mg g
–1
. ZIF-67-0.2 HPW displayed good reusability,
and the adsorption data can be well described by pseudo-second order
and Langmuir isotherm models. The adsorption mechanism was ascribed
to the preferred electrostatic attraction and π–π
stacking between MB and composite adsorbents. This work provides a
route to enhance organic dye removal efficiency of ZIF materials through
regulation of surface charge property and sheds light on the development
of ZIF-based adsorbents.