Selective adsorption and detection of p-arsanilic acid on MOF-on-MOF heterostructure induced by nitrogen-rich self-assembly template

P-arsanilic acid (p-ASA), as a widely used feed additive, is potentially toxic to aquatic organisms and seriously affects the water environment. Therefore, the development of an intelligent multi-functional material for selective simultaneous detection and removal of p-ASA in water has become a top priority. Here, we report one case of novel nitrogen-rich two-dimensional metal–organic framework, Cu(I)-tpp (Htpp = 1-(4-(tetrazol-5-yl))3-(pyrzin-2-yl) pyrazol), which has outstanding fluorescence emission at 655 nm; and nitrogen-rich sites exposed on the surface make it an excellent self-assembly template to induce the formation of heterostructures. According to the target requirements, ZIF-8 is selected to construct the Cu(I)-tpp@ZIF-8 heterostructure by liquid-phase epitaxy ignoring the lattice mismatch problem. And the electronic structure of the Cu(I)-tpp framework is analyzed by electrostatic potential (ESP) to determine the nucleation site of ZIF-8. The prepared Cu(I)-tpp@ZIF-8 heterostructure assembles adsorption and fluorescence sensing properties, exhibiting significant adsorption (q_max = 303.0 mg g⁻¹) and fluorescence quenching response (LOD = 0.4 µg·L⁻¹) for p-ASA. Notably, Cu(I)-tpp@ZIF-8 achieves a special response to p-ASA that is different from other organic arsenic acids, especially compared with its isomer (o-ASA) and roxarsone (ROX). As a smart multifunctional material, Cu(I)-tpp@ZIF-8 realizes the specificity in the simultaneous detection and removal of p-ASA, presenting excellent application prospects in water quality monitoring.