A novel hierarchical porous ZIF-8 for effective removal of three non-steroidal anti-inflammatory drugs simultaneously from environment.

Metal organic frameworks (MOFs) adsorbents have significant advantages to remove contaminates. While their microporous structure is not conducive to entry of larger molecules, making it difficult to simultaneously utilize the inner and outer surfaces of the pores to achieve higher adsorption capacity. In this work, the hexadecyltrimethylammonium bromide was employed as soft template to prepare a novel hierarchical porous ZIF-8 (HP-ZIF-8) in water. The result showed that the developed HP-ZIF-8 has both microporous (0.59 nm) and mesoporous structures (35.59 nm), which is 33 times larger than that of initial ZIF-8 (1.08 nm). Mesoporous HP-ZIF-8 enhances adsorption, enabling simultaneous capture of diclofenac sodium (DFS), flunixin meglumine (FM), and meloxicam (ME). The adsorption process for DFS, FM, and ME was agreement with the Langmuir model, and maximum adsorption capacities were 119.33, 162.87, and 40.45 mg g, respectively. Moreover, the mesopores effectively enhance mass transfer rate, and the adsorption equilibrium can be reached within 10 min. Mechanistic analysis revealed that DFS, FM, and ME adsorption onto HP-ZIF-8 was driven by hydrogen bonding, π-π stacking, electrostatic and metal coordination interactions, alongside mesoporous structure-induced physical adsorption. Furthermore, HP-ZIF-8 was successfully applied in the removal of these pharmaceutical compounds from five different real water samples and three food matrices, achieving recoveries between 84.54% and 106.59%, with relative standard deviations below 4.05%. This work provides a simple and feasible method to improve the adsorption performance of MOFs, making them efficiently adsorbing and removing pollutants from the environment.