Methylene Blue Dye Absorption Studies of PHEMA@MOF801 and PHEMA@MOF303 Hybrid Hydrogel Composites

In this study, hybrid hydrogel composites combining two distinct metal-organic frameworks (MOFs) (MOF801 and MOF303) into a poly(2-hydroxyethyl methacrylate) (PHEMA) matrix are successfully fabricated and evaluated in terms of their pH-responsive swelling and dye adsorption performance. The MOF801 and MOF303 are dispersed into the hydrogel matrix by simple physical blending, ensuring the formation of hybrid materials without chemical bonding. Structural and morphological characterizations are performed using Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy-energy-dispersive X-ray spectroscopy, and thermogravimetric-differential thermal analysis. Swelling behaviors of hydrogels are investigated in solutions with pH values of 3, 7, and 11. Among the tested conditions, the highest swelling ratios are observed at pH 11, with swelling percentages (S%) of 151%, 173%, and 164% for PHEMA, PHEMA@MOF303, and PHEMA@MOF801, respectively. Furthermore, the hydrogels are employed as adsorbents for the removal of cationic dye methylene blue. The dye removal efficiency (W%) is found to be 61.0% for MOF-free PHEMA, 67.6% for PHEMA@MOF801, and 75.0% for PHEMA@MOF303. The corresponding adsorption capacities (q) are calculated as 2.57, 2.43, and 3.95 mg g^-1, respectively. UV-vis spectrophotometry is employed to monitor dye adsorption. These findings demonstrate the synergistic effects between coordination polymers and hydrogel matrices, offering promising insights for the development of responsive and efficient adsorbent materials for wastewater treatment.