Shao-Xian Liu

Robust Crystalline Hybrid Solid with Multiple Channels Showing High Anhydrous Proton Conductivity and a Wide Performance Temperature Range

A proton conductor displaying high anhydrous proton conductivity (≈10(-2) S cm(-1)) and good performance over a broad temperature range is presented. This hybrid material is produced via doping HCl into open-framework chalcogenide(C2N2H10)(C2N2H9)2 Cu8 Sn3S12, and has cubopolyhedral cavities and multiple channels.

Proton Conductance of a Superior Water-Stable Metal–Organic Framework and Its Composite Membrane with Poly(vinylidene fluoride)

Proton-exchange membranes (PEMs) as separators have important technological applications in electrochemical devices, including fuel cells, electrochemical sensors, electrochemical reactors, and electrochromic displays. The composite membrane of a proton-conducting metal-organic framework (MOF) and an organic polymer combines the unique physical and chemical nature of the polymer and the high proton conductivity of the MOF, bringing together the best of both components to potentially fabricate high-performance PEMs. In this study, we have investigated the proton-transport nature of a zirconium(IV) MOF, MOF-808 (1). This superior-water-stability MOF shows striking proton conductivity with σ = 7.58 × 10-3 S·cm-1 at 315 K and 99% relative humidity. The composite membranes of 1 and poly(vinylidene fluoride) (PVDF) have further been fabricated and are labeled as 1@PVDF-X, where X represents the mass percentage of 1 (as X%) in 1@PVDF-X and X = 10-55%. The composite membranes exhibit good mechanical features and durability for practical application and a considerable proton conductivity of 1.56 × 10-4 S·cm-1 in deionized water at 338 K as well. Thus, the composite membranes show promising applications as alternative PEMs in diverse electrochemical devices.

Water assisted high proton conductance in a highly thermally stable and superior water-stable open-framework cobalt phosphate

Proton-conducting materials show important technological applications as key components in energy conversion, electrochemical sensing and electrochromic devices; the exploration for new types of proton-conducting materials is crucial for the development of efficient electrochemical devices. In this study, we investigated the proton transport nature of an inorganic-organic hybrid crystal of open-framework cobalt phosphate, (C2N2H10)0.5CoPO4. The structure of the hybrid crystal consists of the [CoPO4]-∞ anionic framework, and the proton carriers, H2en2+ cations (en = ethylenediamine), are located in the pores to compensate the negative charges of the inorganic framework. The open-framework is thermally stable up to 653 K (380 °C) at least, and also shows superior water stability. The open-framework exhibits negligible conductance in an anhydrous environment even at 473 K; however, there is evident water-assisted proton conduction. The conductivity reaches 2.05 × 10-3 S cm-1 at 329 K and 98% RH. Such high proton conductivity can compete with numerous state-of-the-art MOFs/PCPs-based proton conductors, and this material has promising applications in diverse electrochemical devices.

A Two-Dimensional Inorganic–Organic Hybrid Solid of Manganese(II) Hydrogenophosphate Showing High Proton Conductivity at Room Temperature

The inorganic-organic hybrid metal hydrogenophosphate with a formula of (C2H10N2)[Mn2(HPO4)3](H2O) (1) shows layered crystal structure. The inorganic anion layer is built from Mn3O13 cluster units, and the interlayer spaces are filled by the charge-compensated ethylenediammonium dications together with the lattice water molecules. The thermogravimetry, variable-temperature powder X-ray diffraction, and the proton conductance under anhydrous and moisture environments were investigated for 1, disclosing that 1 shows high thermal stability and high proton transport nature, and the proton conductivity reaches to 1.64 × 10(-3) S·cm(-1) under 99%RH even at 293 K. The high proton conductivity is related to the formation of denser H-bond networks in the lattice.

Insights into understanding water mediated proton conductivity in an intercalated hybrid solid of kaolinite at ambient temperature

In this study, an intercalated hybrid solid of kaolinite with L-alanine (abbr. K-Ala) was prepared, and the proton conductance of K-Ala has been investigated in both anhydrous and humid environments, respectively. The proton conductivity (σ) of K-Ala is 5.38 × 10−8 S cm−1 under an N2 atmosphere (anhydrous environment), while it is much enhanced under humid conditions and σ = 1.35 × 10−4 S cm−1 under 99% relative humidity (RH) at ambient temperature. With increasing temperature, the proton conductivity reaches 2.1 × 10−3 S cm−1 at 99% RH and 318 K, and this σ value is comparable to that recently reported in some of the high proton conducting MOF/PCP materials. DFT calculations were performed for the crystal structures containing different amounts of water molecules within the interlayer spaces of K-Ala, disclosing that the amounts of water molecules strongly influence the H-bond network. A denser H-bond network is formed when there are large amounts of water molecules in the interlayer spaces of K-Ala, providing an efficient proton transport pathway; as a consequence, the proton conductivity of K-Ala is much enhanced at high relative humidity.

Both Dielectrics and Conductance Anomalies in an Open-Framework Cobalt Phosphate

Switchable conducting or dielectric materials, as the key component, show important technological applications in modern electrical and electronic devices, including data communication, phase shifters, varactors, and rewritable optical data storage. To explore new types of switchable conducting or dielectric materials could significantly accelerate the development of efficient electrical and electronic devices. Herein we present the first example of switchable conducting and dielectric material, which is based on an open-framework phosphate, (C2N2H10)0.5CoPO4. A reversible isostructural phase transition occurs at ∼348 K in this open-framework phosphate, to give both dielectrics and conductance anomaly around the critical temperature of phase transition. This study will provide a roadmap for searching new switchable conducting or dielectric materials as well as new applications of open-framework phosphates.

A high temperature reversible phase transition in a supramolecular complex of 15-crown-5 with tetraphenylboron sodium

A supramolecular crystal, [Na(15-crown-5)][BPh4] (1), (15-crown-5 = 1,4,7,10,13-pentaoxacyclopentadecane, NaBPh4 = sodium tetraphenylboron), has been obtained by mixing the ethanol solution of 15-crown-5 and NaBPh4 in the molar ratio of 1 : 1. The crystal structure was determined at 293 K, revealing that two [Na(15-crown-5)]+ cations form a supramolecular dimer via sharing one side-edge of coordination pentagonal pyramids; also, there are significant H-bonding interactions between anions and supramolecularly dimeric cations. Differential scanning calorimetry (DSC) showed that 1 undergoes a reversible first-order phase transition at ca. 391 K (Tc) upon heating, with a thermal hysteresis of 19 K. ΔH and ΔS were estimated to be 6.9 kJ mol−1 and 17.7 J mol−1 K−1, respectively, in the heating run. The variable-temperature powder X-ray diffraction and dielectric spectra were collected, and both disclosed no significant difference between the low- and high-temperature phases. These results suggest that the phase transition is an ordered–disordered type, which probably involves the change of anion configuration.

Dielectric anomaly and giant deuteration effect in a H-bond trimeric co-crystal [4, 4'-Bipyridine]2[1,4-dihydroxybenzene]

ABSTRACT Co-crystal [4,4ʹ-bipyridine]2[1,4-dihydroxybenzene] (1) was prepared by evaporating methanol solution of 4,4ʹ-bipyridine with 1,4-dihydroxybenzene at 4°C. 1 shows a fascinating dielectric anomaly with a maximum at ~210 K, which is independent on ac frequency. However, the absence of thermal anomaly and structural phase transition is related to the dielectric anomaly. The co-crystal [4,4ʹ-bipyridine]2[1,4-dihydroxybenzene-d2] (2) was further obtained via H+/D+ exchange in 1 and the deuteration gives rise to the maximum shifting to 254 K in the dielectric spectrum of 2. The dielectric anomaly corresponds to disorder-to-order transformation of H+/D+ in the O–H/D···N H-bond in 1 and 2.

CCDC 892060: Experimental Crystal Structure Determination

Related Article: Guo-Jun Yuan, Hao Yang, Shao-Xian Liu, Jian-Lan Liu, Xiao-Ming Ren|2014|Dalton Trans.|43|11908|doi:10.1039/C4DT00868E