Precise manipulation of pore sizes in Zr(IV)-Based metal-organic frameworks for enhanced bisphenol a removal from water

Metal-organic frameworks (MOFs) recently gained immense popularity for the adsorption of organic impurities. In this work, the adsorptive separation of bisphenol A (BPA) from aqueous mixtures was explored utilizing three types of zirconium-based MOFs, namely MOF-808, UiO-66, and hierarchically porous UiO-66 (HP-UiO-66). The HP-UiO-66, which was etched by sodium acetate as the terminal ligand, generated large mesopores ranging from 40 to 300 Å due to the departure of partial linkers and metallic clusters. The adsorption ability for BPA increased significantly with the introduction of numerous mesopores onto the HP-UiO-66 framework, even though the surface area of HP-UiO-66 was lower compared to that of the pristine UiO-66 and MOF-808. The study revealed that the maximum adsorption capacities (q) for BPA by HP-UiO-66 reached up to 295.04 mg g⁻¹, which was about 88.5% and 17.4% higher in comparison to UiO-66 and MOF-808, respectively. Furthermore, the q value of HP-UiO-66 was also better than many other previously reported MOF adsorbents. The analysis of possible adsorption mechanisms indicated that physical pore-filling was anticipated as the principal mechanism, attributed to the larger window size and high mesopore surface area of HP-UiO-66. Furthermore, X-ray photoelectron and Fourier transform infrared spectroscopic measurements inferred that the synergetic effects of H-bonding and π-π interactions played crucial roles in BPA capture as well. Overall, this study revealed a structure–property relationship in the Zr-MOFs-based adsorbents and opened up a new avenue to exploit unique MOF platforms for the efficient removal of emerging contaminations in the future.