Green pristine and modified mofs for phosphate capture and release: A delayed dual-linker synthesis approach

We report a green, delayed dual-linker synthesis of zirconium-based Metal organic frameworks (MOFs) using terephthalic (TPA) and pyromellitic (PMA) acids to enhance phosphate recovery and delivery. The screening balanced adsorption capacity, yield, cost, and handling; identifying HGR1-MOF(25)-M (dual-linker) and the single-linker GR2-MOF (80) as top performers. Ultrasonication increased uptake, with the best material reaching Q max > 100 mg-PO₄·g −1 (C₀ ≈ 100 mg-PO₄·L −1 , pH 6). XRD, FTIR, and XPS confirmed phosphate coordination to Zr sites (inner-sphere Zr–O–P). In fixed-bed columns, breakthrough profiles were best captured by the Modified Dose-Response model (R 2 > 0.98), while desorption showed a two-stage pattern consistent with Korsmeyer–Peppas/Elovich behaviour (early burst of weakly bound phosphate followed by diffusion/ligand-exchange control). Regeneration trade-offs were evident: carbonate acted as a gentler eluent, preserving framework features but providing limited P recovery; NaOH achieved higher desorption with greater structural perturbation, particularly for mixed-linker HGR1-MOF(25)-M materials. When MOF-P was mixed into a sand/kaolinite matrix, 30-day water release was ∼21–25 %, positioning these MOFs between polymer/biocomposite SRFs (∼37–47 %) and struvite (∼9 % at 36 d), and highlighting their suitability for moderated slow-release. Overall, mono- and dual-linker green Zr-MOFs offer a scalable, lower-impact route for selective phosphate recovery from wastewater and controlled nutrient delivery in sandy substrates. Future work should address pilot-scale operation, multi-cycle stability, and integrated LCA. • Green synthesis of MOFs for phosphate recovery. • Improvement mechanical properties through dual linker synthesis. • Dual-linker strategy enhanced adsorption capacity and enabled controlled release in two phases. • Phosphate adsorption exceeded Qmax100 mg-PO₄/g, with high yield and low-cost production. • MOFs showed high selectivity, tunable nutrient release profiles, and supporting fertilizer applications.