The selective removal of one ligand in mixed-ligand MOFs upon thermolysis provides a powerful strategy to introduce additional mesopores without affecting the overall MOF structure. By varying the initial ligand ratio, MOFs of the MIL-125-Ti family with two distinct hierarchical pore architectures are synthesized, resembling either large cavities or branching fractures. The performance of the resulting hierarchically porous MOFs is evaluated toward the adsorptive removal of glyphosate (N-(phosphonomethyl)glycine) from water, and the adsorption kinetics and mechanism are examined. Due to their strong affinity for phosphoric groups, the numerous Ti-OH groups resulting from the selective ligand removal act as natural anchor points for effective glyphosate uptake. The relationships between contact duration, glyphosate concentration, and adsorbent dosage are investigated, and the impact of these parameters on the effectiveness of glyphosate removal from contaminated water samples is examined. The introduction of additional mesopores has increased the adsorption capacities by nearly 3 times with record values exceeding 440.9 mg g −1 , which ranks these MOFs among the best-reported adsorbents.
Glyphosate removal from contaminated water by natural clay, natural zeolite, commercial kaolin, bentonite, and sepiolite was compared. Natural clay showed high removal efficiency next to purified kaolin. The adsorption data for natural clay better fitted the Langmuir isotherm model and pseudo-second-order kinetic model. The adsorbent dose was found to be the most important process parameter while the pH did not exhibit any significant effect. An optimization study allowed achieving the highest removal efficiency and sorption capacity. The correlation coefficient R 2 of the regression model indicated that the observed results fitted well with the model prediction.
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