Construction of porous channels in electrospun Bi-MOF/polymer composite fiber membrane for enhanced arsenate removal from water

• Hierarchical porous Bi-MOF fiber (MOF@PPAN-3) was fabricated via electrospinning. • Bi-MOF and MOF@PPAN-3 exhibited selective adsorption of arsenate. • Stable adsorption capacity over a wide pH range. • A synergetic adsorption mechanism of arsenate for Bi-MOF was proposed. • Reaction of arsenate ions with Bi metal sites to form Bi-O-As bonds. Arsenic (As) contamination in water poses a serious threat to human health and the natural environment due to its carcinogenicity and toxicity. Developing efficient adsorbents for arsenic removal is crucial to addressing this issue. In this research, a bismuth-based metal–organic framework (Bi-MOF, CAU-17) was synthesized, and electrospun hybrid MOF/polymer composite fibers (MOF@PPAN-3) with mesoporous structures by selectively removing polyvinylpyrrolidone. The MOF particles were immobilized in the polymer matrix to prevent secondary contamination and enhance recoverability, while mesoporous channels in the fibers increased arsenate exposure to the MOF adsorption sites. Adsorption experiments demonstrated that both CAU-17 and the composite fibers demonstrated remarkable efficiency in removing As(V), and the adsorption behavior was more consistent with the pseudo-second-order model, achieving theoretical maximum adsorption capacities of 183.67 mg/g and 69.01 mg/g, respectively. The materials exhibited excellent stability across a wide pH range (3-11), high selectivity against competing anions, and a certain degree of reusability over multiple cycles. Characterization results revealed that the adsorption mechanism was attributed to a synergistic effect of ligand exchange and surface complexation at the metallic Bi sites in the MOF. Additionally, Density functional theory calculations demonstrated that arsenate anions could be immobilized within the three types of channels in CAU-17, forming stable Bi-O-As bonds. These findings highlight the potential of CAU-17 and MOF@PPAN-3 fiber membranes for efficient arsenic removal from water.