Tuning Surface Functionalization and Pore Structure of UiO-66 Metal–Organic Framework Nanoparticles for Organic Pollutant Elimination

PPCPs (pharmaceuticals and personal care products) have aroused great concern because of their potential toxicities in human beings and ecosystems. A lot of effort has been done for their effective elimination. However, their diverse structures are still the main challenges. Metal–organic frameworks (MOFs) show great potential because they can be designed based on the specific demand. Deeply understanding the interaction mechanisms between PPCPs and MOFs systematically is of great demand for nanomaterial development in the future. Among the large MOFs families, Zr-based ones, which contain designable node connectivity, outstanding stability, and intriguing properties, have been considered as one of the most attractive candidates for micropollutants removal and detoxification. Also, it can offer an ideal platform to study the structure and activity relationship systematically. In this study, we designed a series of Zr-based MOFs with different surface functional groups (defective UiO-66 (D-UiO-66), UiO-67, and a series of UiO-66-R MOFs derivatives). Representative pharmaceuticals with totally opposite chemical properties ibuprofen (IBU) and carbamazepine (CBZ) were chosen as the model compounds. In order to prove our concept of electrostatic interaction, we precisely designed a defective rich MOF material (Zr₆O₄(OH)₄(BDC)_3.9) which is positive charged in the central Zr node. The defective structure in UiO-66 (3.9 BDC linkers) can significantly accelerate kinetics with a v₀ value of 558.42 mg/(g·min), indicating the strong electrostatic interaction. In contrast, for CBZ, π–π interaction and hydrophobic interaction are the two main mechanisms. Additionally, FTIR, ζ potential, and XPS analysis have been conducted to gain insight into this interaction. With simple modification, the adsorption performance of micropollutants can be facilitated significantly. Besides, this material can be easily regenerated by an environmentally friendly approach without changing crystallinity and porosity throughout five adsorption and desorption cycles. Our findings offer a useful guidance for adsorbent design.