Zeolitic Imidazolate Framework-8 (ZIF-8), for the first time for ZIFs, exhibits a remarkable capacity for the anticancer drug 5-fluorouracil (5-FU), around 660 mg of 5-FU/g of ZIF-8, and presents a pH-triggered controlled drug release property. These prove ZIF-8 to be a valuable candidate for delivery of anticancer agents and reveal its potential applications in the treatment of cancer.

Two novel polyoxometalate (POM)-based metal-organic frameworks (MOFs), [TBA]3[ε-PMo(V)8Mo(VI)4O36(OH)4Zn4][BTB]4/3·xGuest (NENU-500, BTB = benzene tribenzoate, TBA(+) = tetrabutylammonium ion) and [TBA]3[ε-PMo(V)8Mo(VI)4O37(OH)3Zn4][BPT] (NENU-501, BPT = [1,1'-biphenyl]-3,4',5-tricarboxylate), were isolated. In these compounds, the POM fragments serving as nodes were directly connected with organic ligands giving rise to three-dimensional (3D) open frameworks. The two anionic frameworks were balanced by TBA(+) ions residing inside the open channels. They exhibit not only good stability in air but also tolerance to acidic and basic media. Furthermore, they were employed as electrocatalysts for the hydrogen evolution reaction (HER) owing to the combination of the redox activity of a POM unit and the porosity of a MOF. Meanwhile, the HER activities of ε(trim)(4/3), NENU-5, and HKUST-1 were also studied for comparison. Remarkably, as a 3D hydrogen-evolving cathode operating in acidic electrolytes, NENU-500 exhibits the highest activity among all MOF materials. It shows an onset overpotential of 180 mV and a Tafel slope of 96 mV·dec(-1), and the catalytic current density can approach 10 mA·cm(-2) at an overpotential of 237 mV. Moreover, NENU-500 and NENU-501 maintain their electrocatalytic activities after 2000 cycles.

Imidazole molecules were frequently incorporated into porous materials to improve their proton conductivity. To investigate how different arrangements of imidazoles in metal-organic frameworks (MOFs) affect the overall proton conduction, we designed and prepared a MOF-based model system. It includes an Fe-MOF as the blank, an imidazole@Fe-MOF (Im@Fe-MOF) with physically adsorbed imidazole, and an imidazole-Fe-MOF (Im-Fe-MOF), which contains chemically coordinated imidazole molecules. The parent Fe-MOF, synthesized from the exchange of carboxylates in the preformed [Fe(μ-O)](carboxylate) clusters and multitopic carboxylate ligands, serves as a control. The Im@Fe-MOF was prepared by encapsulating free imidazole molecules into the pores of the Fe-MOF, whereas the Im-Fe-MOF was obtained in situ, in which imidazole ligands coordinate to the metal nodes of the framework. Proton-conductivity analyses revealed that the proton conductivity of Im-Fe-MOF was approximately two orders of magnitude greater than those of Fe-MOF and Im@Fe-MOF at room temperature. The high proton conductivity of 1.21 × 10 S cm at 60 °C for Im-Fe-MOF ranks among the highest performing MOFs ever reported. The results of the density functional theory calculations suggest that coordinated imidazole molecules in Im-Fe-MOF provide a greater concentration of protons for proton transportation than do coordinated water molecules in Fe-MOF alone. Besides, Im-Fe-MOF exhibits steadier performance than Im@Fe-MOF does after being washed with water. Our investigation using the above ideal crystalline model system demonstrates that compared to disorderly arranged imidazole molecules in pores, the immobilized imidazole molecules by coordination bonds in the framework are more prone to form proton-conduction pathways and thus perform better and steadier in water-mediated proton conduction.

A facile, cost-effective and sensitive colorimetric detection method for Pb(2+) has been developed by using glutathione functionalized gold nanoparticles (GSH-GNPs). The sensitivity and selectivity of detection were investigated in detail. The GSH-GNPs could be induced to aggregate immediately in the presence of Pb(2+), especially after the addition of 1 M NaCl aqueous solution. The Pb(2+) could be detected by colorimetric response of GNPs that could be monitored by a UV-vis spectrophotometer or even naked eyes, and the detection limit could reach 100 nM. The GSH-GNPs bound by Pb(2+) showed excellent selectivity compared to other metal ions (Hg(2+), Mg(2+), Zn(2+), Ni(2+), Cu(2+), Co(2+), Ca(2+), Mn(2+), Fe(2+), Cd(2+), Ba(2+), and Cr(3+)), which led to prominent color change. This provided a simple and effective colorimetric sensor (no enzyme or DNA) for on-site and real-time detection of Pb(2+). Most importantly, this probe was also applied to determine the Pb(2+) in the lake samples with low interference and high sensitivity.