Rational Functionalization of UiO-66 with Pd Nanoparticles: Synthesis and In Situ Fourier-Transform Infrared Monitoring.

Functionalization of metal-organic frameworks (MOFs) with noble metal nanoparticles (NPs) is a challenging task. Conventional impregnation by metals often leads to agglomerates on the surface of MOF crystals. Functional groups on linkers interact with metal precursors and promote the homogeneous distribution of NPs in the pores of MOFs, but their uncontrolled localization can block channels and thus hinder mass transport. To overcome this problem, we created nucleation centers only in the defective pores of the UiO-66 MOF via the postsynthesis exchange. First, we have introduced defects into UiO-66 using benzoic acid as a modulator. Second, the modulator was exchanged for amino-benzoic acid. As a result, amino groups have decorated mainly the defective pores and attracted the Pd precursor after impregnation. The interaction of the metal precursor with amino groups and the growth of NPs were monitored by in situ infrared spectroscopy. Three processes were distinguished: the gaseous HCl release, NH2 reactivation, and growth of extended Pd surfaces. Uniform Pd NPs were located in the pores because of the homogeneous distribution of the precursor and pore diffusion-limited nucleation rate. Our work demonstrates an alternative approach of controlled Pd incorporation into UiO-66 that is of great importance for the rational design of heterogeneous catalysts.

A heterostructural MoS2QDs@UiO-66 nanocomposite for the highly efficient photocatalytic degradation of methylene blue under visible light and simulated sunlight.

The development of recyclable photocatalysts with high activity and stability has piqued the interest of researchers in the field of wastewater treatment. In this study, an ultrasonic probe approach was used to immerse a sequence of heterojunctions formed by metal-organic frameworks (UiO-66) and different amounts of molybdenum disulfide quantum dots (MoS2QDs), resulting in a highly recyclable MoS2QDs@UiO-66 photocatalyst. Multiple advanced techniques, such as XPS, XRD, TEM, XRF, and UV-vis spectrophotometry, were used to characterize and confirm the successful preparation of UIO-66 impregnated with MoS2QDs. The results indicated that the best heterostructure catalyst exhibited superior efficiency in the photocatalytic degradation of methylene blue (MB) in water, achieving approximately 99% removal within 30 minutes under simulated sunlight, while approximately 97% removal under visible light. The outstanding photocatalytic performance is predominantly attributed to the photoinduced separation of carriers in this heterostructure system. This study proposes a unique, simple, and low-cost method for improving the degradation performance of organic contaminants in water.