RESUMO
We report the fabrication of macroscopically and microscopically homogeneous, crack-free metal-organic framework (MOF) UiO-66-NH2 (UiO: Universitetet i Oslo; [Zr6 O4 (OH)4 (bdc-NH2 )6 ]; bdc-NH2 2- : 2-amino-1,4-benzene dicarboxylate) thin films on silicon oxide surfaces. A DMF-free, low-temperature coordination modulated (CM), layer-by-layer liquid phase epitaxy (LPE) using the controlled secondary building block approach (CSA). Efficient substrate activation was determined as a key factor to obtain dense and smooth coatings by comparing UiO-66-NH2 thin films grown on ozone and piranha acid-activated substrates. Films of 2.60â µm thickness with a minimal surface roughness of 2â nm and a high sorption capacity of 3.53â mmol g-1 MeOH (at 25 °C) were typically obtained in an 80-cycle experiment at mild conditions (70 °C, ambient pressure).
RESUMO
Metal-organic frameworks (MOFs) and their derivatives are considered as promising catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which are important for many energy provision technologies, such as electrolyzers, fuel cells and some types of advanced batteries. In this work, a "strain modulation" approach has been applied through the use of surface-mounted NiFe-MOFs in order to design an advanced bifunctional ORR/OER electrocatalyst. The material exhibits an excellent OER activity in alkaline media, reaching an industrially relevant current density of 200â mA cm-2 at an overpotential of only ≈210â mV. It demonstrates operational long-term stability even at a high current density of 500â mA cm-2 and exhibits the so far narrowest "overpotential window" ΔEORR-OER of 0.69â V in 0.1 m KOH with a mass loading being two orders of magnitude lower than that of benchmark electrocatalysts.
RESUMO
Here we report on the synthesis, structure, and characterization of the first example of a polyoxopalladate (POP)-based metal-organic framework (MOF). This novel class of materials comprises discrete polyoxo-13-palladate(II) nanocubes [Pd13O8(AsO4)8H6]8- decorated by four Ba2+ ions on each of two opposite faces. These secondary building units (SBUs) are linked to each other via rigid linear organic groups, resulting in a stable 3D POP-MOF framework, which exhibits interesting sorption as well as catalytic properties.