Porous La2O2CO3 derived from solvent-guided metal-organic frameworks for high-efficient phosphorus removal

Abstract

La-based materials have garnered considerable attention as potential adsorbents for phosphate removal because they capture phosphate with high affinity, producing an ultralow phosphorous-concentration output. Herein, La-based metal–organic frameworks (La–MOFs, La-1,3,5-benzentricarboxylate) with tunable structures were fabricated by regulating the coordination solvent environment, which largely determines both the pore structure and chemical components of their corresponding La2O2CO3 derivatives and the phosphate adsorption performance. A porous La2O2CO3 derivative (W–D T500) derived from the water/N,N-dimethylformamide (DMF) guided La–MOF showed abundant mesopores and a high surface area, because the pore-opening degree under high-temperature pyrolysis is higher in W–D T500 than in the La2O2CO3 derivative obtained from the water/ethanol solvent–guided La–MOF. W–D T500 also had higher La (78.3%) and carbonate contents of the crystal structure owing to the higher efficiency of carbon conversion to carbonate-oxides in W–D T500. Consequently, the porous La2O2CO3 derivative W–D T500 exhibited superior phosphate adsorption capacity (91.6 mg P/g), high adsorption selectivity, and excellent recycling performance. Phosphate was attached to the La2O2CO3 adsorbents via a ligand-exchange mechanism between phosphate and CO32−/–OH. This study provides a solvent guidance strategy to construct functional La–MOFs and La2O2CO3 derivatives for excellent phosphate removal.