Perspectives on metal–organic frameworks with intrinsic electrocatalytic activity

Associate Professor Deanna D

A/Prof Deanna D'Alessandro

August 2017
Marcello solomon, Tamara Church and Deanna D'Alessandro* et al. CrystEngComm, 19 29, 4049-4065, 2017. DOI: 10.1039/c7ce00215g

This highlight article focuses on the rapidly emerging area of electrocatalytic metal-organic frameworks (MOFs) with a particular emphasis on those systems displaying intrinsic activity. Three electrocatalytic conversion processes are discussed, including CO2 reduction, the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), as well as a selection of other relevant examples. The scope of our discussion encompasses aspects of MOF structure that are key to their function, performance characteristics such as stability and selectivity, together with methods for interfacing MOFs with surfaces. Key challenges that have emerged are highlighted in addition to opportunities that are relevant to the field in the design of more stable, selective and robust electrocatalysts for a range of industrial processes.

Fluorinated tripodal receptors for potentiometric chloride detection in biological fluids

Professor Phil Gale

Prof Phil Gale

August 2017
Laura Jowett, Ethan Howe and Philip Gale et al. Biosensors and Bioelectronics, 99, 70-76, 2017. DOI: 10.1016/j.bios.2017.07.001

Fluorinated tripodal compounds were recently reported to be efficient transmembrane transporters for a series of inorganic anions. In particular, this class of receptors has been shown to be suitable for the effective complexation of chloride, nitrate, bicarbonate and sulfate anions via hydrogen bonding. The potentiometric properties of urea and thiourea-based fluorinated tripodal receptors are explored here for the first time, in light of the need for reliable sensors for chloride monitoring in undiluted biological fluids. The ion selective electrode (ISE) membranes with tren-based tris-urea bis(CF3) tripodal compound (ionophore I) were found to exhibit the best selectivity for chloride over major lipophilic anions such as salicylate and thiocyanate. Ionophore I-based ISEs were successfully applied for chloride determination in undiluted human serum as well as artificial serum sample, the slope of the linear calibration at the relevant background of interfering ions being close to Nernstian (49.8±1.7 mV). The results of potentiometric measurements were confirmed by argentometric titration. Moreover, the ionophore I-based ISE membrane was shown to exhibit a very good long-term stability of potentiometric performance over the period of 10 weeks. Nuclear magnetic resonance (NMR) titrations, potentiometric sandwich membrane experiments and density functional theory (DFT) computational studies were performed to determine the binding constants and suggest 1:1 complexation stoichiometry for the ionophore I with chloride as well as salicylate.

Small angle neutron scattering study of the conformation of poly (ethylene oxide) dissolved in deep eutectic solvents

Professor Greg Warr

Prof Greg Warr

August 2017
Paul FitzGerald and Greg Warr et al. Journal of Colloid and Interface Science, 506, 486-492, 2017. DOI: 10.1016/j.jcis.2017.07.068

Hypothesis: The conformation of poly(ethylene oxide) (PEO) in deep eutectic solvents (DESs) is determined by the polymer–solvent interactions, especially hydrogen bonding interactions. The hypothesis for this work is that the hydrogen bonding environment of a DES can be varied via changing the cation or hydrogen bond donor (HBD), and therefore the solvent quality for PEO; the anion species will also effect hydrogen bonding, but this is not examined here.

Experiments: Small angle neutron scattering (SANS) is used to probe the concentration dependent conformation of 36 kDa PEO dissolved in DESs formed by mixing ethyl or butyl ammonium bromide with a molecular HBD (glycerol or ethylene glycol) in a 1:2 molar ratio.

Findings: The radius of gyration (Rg), Flory exponent and crossover concentration (c*) from the dilute to the semi-dilute regime of PEO in the DESs revealed by SANS and Zimm plot analysis show that these DESs are moderately good solvents for PEO. When the ammonium alkyl chain length is increased, the hydrogen bond density per unit volume decreases, and with it the solvent quality for PEO. The solvent quality is improved when the HBD is changed from glycerol to ethylene glycol due to differences in the hydrogen bonding environment for PEO.

Renewable aromatics from Kraft lignin with molybdenum-based catalysts

Professor Thomas Maschmeyer

Prof Thomas Maschmeyer

August 2017
Lisa Cattelan, Alexander Yuen, Matthew Lui, Anthony Masters and Thomas Maschmeyer* et al. CHEMCATCHEM, 9 4, 2717-2726, 2017. DOI: 10.1002/cctc.201700374

The catalytic depolymerization of Kraft lignin in supercritical ethanol was explored in the presence of Mo2C- and MoS2-based catalysts. At 280 8C, Mo2C and Mo2C/Al2O3 afforded aromatic yields of 425 and 419 mgg@1 lignin, respectively: amongst the highest yields reported to date. Ionic–liquid–assisted delamination of MoS2 resulted in highly active catalysts, capable of quantitative conversion of lignin at the expense of aromatic yield (approximately 186 mgg@1 lignin). Across all the catalysts studied, between 0.04 wt% and 0.38 wt% of molybdenum leached into the solution under supercritical conditions, according to inductively coupled plasma (ICP) analyses (corresponding to 27–570 mg of molybdenum in the reaction supernatant). A small contribution to the molybdenum in solution comes from the reactor itself (HastelloyC contains 16 wt% Mo). Analysis of a depolymerization performed with fresh Kraft lignin and the soluble portion of the reaction mixture from a previous reactor run indicated that the leached species were neither active enough to afford the high conversions observed, nor selective enough to give high yields of aromatic products. In conjunction with the ICP data and differential chemoselectivities of the Mo2C- and MoS2 based catalysts, these results suggest that the bulk of the catalysis is heterogeneous.

Tri-functional OER, HER and ORR electrocatalyst electrodes from in situ metal-nitrogen Co-doped oxidized graphite rods

Emeritus Professor Len Lindoy

E/Prof Len Lindoy

August 2017
Emeritus Professor Len Lindoy et al. Bulletin of the Chemical Society of Japan, 90 8, 950-954, 2017. DOI: 10.1246/bcsj.20170102

In contrast to monofunctional electrocatalysts for oxygen evolution reaction (OER), hydrogen evolution reaction (HER) or oxygen reduction reaction (ORR), trifunctional catalysts for simultaneously generating H2, O2 and H2O provide a crucial means for improving the overall efficiency of water electrolysis. Herein we present a series of nonnoble metal [M = Fe(III), Co(II), Ni(II)]-nitrogen co-doped oxidized graphite rods (M-N/OGRs) that function as in situ working electrodes for tri-functional OER, HER and ORR electrocatalysis. The enhanced performance of the hybrid catalysts appear mostly associated with dual active site mechanisms originating from the synergic effects of M-N/Co-doped on the surface of the OGR. Our findings suggest that, the development of multifunctional electrocatalysts with optimal catalytic activity using transition metals and nitrogen doped OGR opens new doors for in situ synthesized electrocatalysts for use in clean electrochemical energy storage and conversion technologies.