Selective and superior capture of phosphate by using bimetallic bismuth-based metal-organic frameworks

In order to mitigate the negative impact of aquatic organism eutrophication and maintain the balance of the water ecosystem, the removal of phosphate has become an urgent need. Herein, we prepared two kinds of high-performance bismuth-based metal-organic frameworks (Bi-MOFs) for phosphate treatment, namely, original Bi-MOF (CAU-17) and lanthanum-doped bimetallic Bi-MOF (La-CAU-17). The maximum adsorption capacity of as-made CAU-17 attains 186.57 mg/g. Noticeable, the maximum adsorption capacity of La-CAU-17 is up to 216.07 mg/g due to the doping of lanthanum. The experimental result shows that La-CAU-17 has a better affinity for phosphate and maintains a higher adsorption capacity in a wide pH range (7-12). Mechanistic studies supported by fourier transform infrared spectroscopy (FTIR) have shown that the binder BTC3- and La3+ could coordinate during the doping process, thus exposing more central metal (Bi) as the adsorption sites. Furthermore, density functional theory (DFT) calculation demonstrates that La-CAU-17 has more negative adsorption energy, which is more conductive to phosphate adsorption. In conclusion, bimetallic Bi-MOF (La-CAU-17) has a synergistic effect on phosphate adsorption and provides a candidate method for efficient and selective adsorption of phosphate.