Architecting polyoxovanadate-based POMOF adsorbent for specific removal of creatinine

A new polyoxovanadates-based metal-organic framework (POV-MOF) Ag₂(Tipa)₂(V₆O₁₆) (Ag-V-MOF) with unique curly layered structure has been designed by virtue of a stellated tridentate N-containing ligand of tri-(4-(1-H-imidazol-1-yl)phenyl)amine (Tipa). After effectually alkali-treated by sodium hydroxide solution in certain concentrations, the modified materials, named EA_x-Ag-V (x = 1, 2, 3, and 4) were obtained expectedly, among which EA₃-Ag-V exhibited a gratifying performance in adsorption creatinine, a major uremic toxin generated during hemodialysis treatment in patients with renal failure. The maximum adsorption capacity of creatinine was 140.45 mg g^-1 for EA₃-Ag-V, and it also displayed a good reusability and stable adsorption performance in a wide pH range. In this work, two statistical models of definitive screening design (DSD) and central composite rotatable design (CCRD) were applied effectively to determine the effect of mixed co-existing substances to the adsorption process. Based on the batches of experiments and characteristic measurements, as well as fractal dimension analyses of the materials, the underlying adsorption mechanism between creatinine and EA₃-Ag-V was detailedly revealed, including π-π interaction, H-bonding force, and electrostatic attraction.