Synthesis of zirconium oxycarbide powders using metal–organic framework (MOF) compounds as precursors

Abstract

ZrC x O y oxycarbides were synthesized for the first time by using Metal-Organic Framework (MOF) compounds as precursors. These MOFs, based on zirconium carboxylates, are derived from the UiO-66 type structure. Three different Zr-MOF compounds were synthesized, differing by their C/Zr ratio, due to the use of terephthalic acid (C/Zr=8, or UiO-66), naphtalene-2,6-dicarboxylic acid (C/Zr=12) and biphenyl-4,4'-dicarboxylic acid (C/Zr=14 or UiO-67). The oxycarbides crystallites obtained through appropriate thermal treatments (under Ar atmosphere) of the Zr-MOF precursors show an average size of few hundred microns. They are surrounded by an outer rim of turbostratic carbon, which thickness is directly relevant to the C/Zr ratio coming from the nature of the organic linker. The composition of the oxycarbides obtained was estimated on the basis of the cell parameters refined from the powder XRD patterns. The oxycarbides synthesized from naphtalene-2,6dicarboxylic acid and biphenyl-4,4'-dicarboxylic acid are close to ZrC 0.925 O 0.075 , while that of the oxycarbide obtained from terephthalic acid precursor is ZrC 0.944 O 0.056 . It results that the carbon richer oxycarbide product is observed for the UiO-66 precursor synthesized with terephthalic acid, and exhibiting the lower C/Zr ratio of the series. The composition of the oxycarbide powders is shown to be directly relevant to the mechanisms of decomposition of the Zr-MOF compound involved during heating.

Conformal Functionalization of Cotton Fibers via Isoreticular Expansion of UiO-66 Metal-Organic Frameworks

“…Furthermore, well defined diffraction peaks ascribed to Zirconium MOFs are observed at lower angles (between 5 • and 14 • ). The pattern of the specimens quantitatively agrees with those reported in the literature for powdered UiO-66 [15], UiO-66-NDC [38], and UiO-67 [24], and also agrees with PXRD simulations of the respective MOFs showed in dotted lines in Figure 3. UiO-66-NH 2 is isostructural with UiO-66 [24]; therefore, the diffraction peaks for cotton+UiO-66 and cotton+UiO-66-NH 2 show the same diffraction peak positions.…”

Zirconium oxycarbides and oxycarbonitrides: A review

“…In addition, Zr-based photosensitive resin was used as a material for 3D printing of octet truss precursors, which were later pyrolyzed under nitrogen at 600-1200 • C. 72 In another study, zirconium carboxylates as metal-organic framework compounds were used to synthesize ZrCO. 73 The precursors were annealed in a graphite furnace at 1750 • C for 8 h under argon atmosphere. Additionally, zirconium oxycarbides were prepared as intermediate anode products during the production of zirconium nanopowders or thin layers by electrochemical methods.…”

“…At the final stage of carbothermal reduction of ZrO 2 (Δm/m 0 > 32%), the authors observed a remarkable increase in a related to the transformation of oxycarbide to carbide, where the expansion of the unit cell was due to the larger atomic radius of C than O and the longer bond length of Zr-C than Zr-O. 32 (4) Transmission electron microscopy investigations coupled with energy-dispersive X-ray spectroscopy 73,87 or electron energy loss spectroscopy (EELS) 24 are used for the local determination of elements. In particular, EELS enables analysis on the nano-and microstructural levels.…”

Zirconium Oxycarbide: A Highly Stable Catalyst Material for Electrochemical Energy Conversion

“…[25] Recently, differential electrochemical mass spectrometry (DEMS) investigations of the ethanol oxidation reaction (EOR) in acidic electrolytes have shown that TiO x C y is a synergistic support for Pt nanoparticles and significantly enhances the CO 2 conversion efficiency at room temperature. [26] As another example, the synthesis and characterization of zirconium oxycarbide powders have been reported in various studies [27][28][29][30] . In a recent work, phase pure zirconium oxycarbide nanopowders (ZrO x C y ) of defined C/Zr ratio have been successfully synthesized via a hybrid solid-liquid synthesis route, [30] which resulted in an electrode material with good electrical conductivity and thus makes ZrO x C y nanopowders an interesting material for electrocatalysis studies as well.…”