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Two-dimensional (2D) π-conjugated conductive metal–organic frameworks (cMOFs, 2DπcMOF) with modulated channel sizes and a broad conductivity range have been reported in the last decade. In contrast, the corresponding comparative studies on their effects on chemiresistive sensing performances, which measure the resistive response toward external chemical stimuli, have not yet been reported. In this work, we sought to explore the structure–performance relationships of honeycomb-like 2D π-conjugated cMOF chemiresistive gas sensors with channel sizes less than 2 nm (the mass transport issue) and broad conductivity in the range from ∼10−8 S cm−1 to 1 S cm−1 (the charge transport issue). As a result, we found that the cMOF with a lower conductivity facilitates the much more sensitive response toward the charge transfer of the adsorbed gases (relative increases in resistance: R = 63.5% toward 100 ppm of NH3 for the as prepared Cu–THQ sensor with the conductivity of ∼10−8 S cm−1). Interestingly, the cMOF with a medium channel size (Cu–THHP–THQ) exhibited the fastest response speed in sensing, although it contains H2en2+ as neutralizing counterions in the channels. From the evaluation of the pore size distribution, it is found that the overall porosity (meso- & micro-pores) of cMOFs, rather than the pore size of the honeycomb structure, would determine their sensing speed. When comparing the performance of two different morphologies of nanorods (NRs) and nanosheets (NSs), NRs showed a slower response and extended recovery time, which can be ascribed to the slower gas diffusion in the more extended 1D channel. Altogether, our results demonstrate the first systematic studies on the effect of various structural parameters on the chemiresistive sensor performance of cMOFs.

We first report the facile synthesis of metal-carbon composites consisting of metal nanoparticles (NPs) and different types of carbon species: onion-like and amorphous carbon, Ni@onion-like carbon and Co@amorphous carbon. By simply changing the metal species in an isostructural metal-organic framework, thermal decompositions of MOF-74 directly afforded different types of metal NPs and carbon composites, which exhibited good electrical conductivity. In particular, the Ni@onion-like carbon, having a well-ordered carbon structure, had high electrical conductivity (sigma = 5.3 omega(-1) cm(-1) at 295 K), explained by a modified model of the Efros-Shklovskii variable range hopping.

The reverse water-gas shift (RWGS) reaction is an important reaction from the viewpoint of converting CO2 into CO as an important raw material compound. As the RWGS reaction is a mildly endothermic and competitive reaction with CO2 methanation, it is important to improve the activity at low temperatures. Here, we report PtW nanoparticles (NPs) supported on γ-Al2O3 (PtW NPs/Al2O3) in which Pt and W were randomly mixed for obtaining a highly active and selective catalyst for the RWGS. At low temperatures of 200 and 300 °C, PtW NPs/Al2O3 exhibited 16- and 17-times higher activity than Pt/Al2O3, one of the most promising catalysts. The enhanced activity of PtW NPs originated from alloying Pt with W, which contributes to the sintering resistance of Pt NPs, and promotion of CO2 adsorption and CO desorption on the catalyst. Furthermore, PtW NPs/Al2O3 exhibited high durability and excellent catalytic performance.

We report the synthesis of MoRu solid-solution alloy nanoparticles using carbonyl complexes as a precursor through thermal decomposition. Alloying Ru with an early transition metal, Mo, leads to an electronic structure change, resulting in an enhancement of the catalytic activity for the hydrogen evolution reaction, which overtook that of the Pt catalyst.

Au and Ru are elements that are immiscible in the bulk state and have the largest gap in reduction potential among noble metals. Here, for the first time, Au x Ru1-x solid-solution alloy nanoparticles (NPs) were successfully synthesized over the whole composition range through a chemical reduction method. Powder X-ray diffraction and scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy showed that Au and Ru atoms are homogeneously mixed at the atomic level. We investigated the catalytic performance of Au x Ru1-x NPs for the oxygen evolution reaction, for which Ru is well known to be one of the best monometallic catalysts, and we found that even alloying with a small amount of Au could significantly enhance the catalytic performance.

We succeeded in controlling the crystal structure of osmium (Os) nanoparticles (NPs). Although Os adopts only a hexagonal close-packed (hcp) structure in the bulk state, a face-centred cubic (fcc) Os was synthesized by a chemical reduction method using an Os acetylacetonate complex as a precursor.

Variable temperature synchrotron powder diffraction methods have been used to study the structures and phase transitions in a series of perovskites of composition Sr1−xBaxHfO3. We find that increasing the Ba content results in a transition from the orthorhombic Pnma type structure to the cubic Pmmvia two intermediate phases, Imma and I4/mcm, as follows:The identification of the correct symmetry has relied on a combination of the observed splitting of the main Bragg reflections and the systematic absence of weak superlattice reflections. Variable temperature diffraction measurements have been used to establish the nature of the various phase transitions (continuous or first order) and these generally are consistent with group theoretical analysis. Unusual behavior is observed for the two compositions Sr0.5Ba0.5HfO3 and Sr0.8Ba2HfO3 at low temperatures.

By adopting a ligand-based solid solution approach, the sulphonic acid functional group can be successfully incorporated into a porous coordination polymer with UiO-66 structure type. Zr(6)O(4)(OH)(4)(BDC-SO(3)H)(1.1)(BDC)(4.9) possesses enhanced heat of adsorption for carbon dioxide and acetone compared to Zr(6)O(4)(OH)(4)(BDC)(6).