Microwave/Ultrasound‐Assisted Synthesis of an Fe(III) Coordination Polymer Derived From an Oxazolone Linker for Adsorptive Removal of 2,4,5‐Trichlorophenoxyacetic Acid

ABSTRACT A novel Fe (III) coordination polymer, was synthesized rapidly via a microwave/ultrasonication method utilizing the organic linker O‐HetCur‐CO and characterized using FT‐IR, powder x‐ray diffraction (PXRD), scanning electron microscopy (SEM)/EDX, x‐ray photoelectron spectroscopy (XPS), TGA, and density functional theory (DFT) computations. The linker and polymer were produced with yields of > 70%. The reaction to form the polymer took place in approximately 5 min at 70°C. Structural characterization methods confirm that coordination has occurred between Fe and the linker (stronger than expected). TGA results indicate that the Fe‐(O‐HetCur‐CO) coordination polymer (FeCP) is stable to ∼340°C. EDX data (weight percentages) show that the final polymer composition consists of C (72.50%), N (9.64%), O (12.75%), and Fe (5.11%). DFT calculations show that coordination with Fe significantly alters electronic properties of the linker: Band gap changes from 2.1410 to 3.9002 eV; the dipole moment changes from 5.5337 to 8.4542 D. Thus, the Fe coordination increases the polarity and structural stability of the final polymer. FeCP adsorption studies of 2,4,5‐T showed rapid uptake to equilibrium within 60 min at concentrations ranging from 10 to 50 ppm. The Langmuir isotherm model produced an excellent fit of equilibrium data ( R 2 = 0.9999) with a maximum adsorption capacity of 54.9 mg g − 1 , K L = 0.1689 L mg − 1 and R L = 0.10 indicating a highly favorable monolayer adsorption process; whereas, the Freundlich model yielded K F = 1.175, n = 0.361 and R 2 = 0.9219 revealing that the surface is heterogeneous but with a dominant chemical adsorption phenomenon. Adsorption studies theoretically validated the experimental results in that FeCP/2,4,5‐T adducts displayed a significant reduction in their band gap (1.9100 eV), an increase in dipole moment (11.43 D), and an electrophilicity index (41.2571 eV). All indicative of strong interfacial electron coupling and donor/acceptor interaction. Also of note, FeCP maintained satisfactory adsorption efficiency after five consecutive adsorption cycles, indicating its great promise for herbicide remediation from pollutant‐laden water.