Cu/Cux S-Embedded N,S-Doped Porous Carbon Derived in Situ from a MOF Designed for Efficient Catalysis

Three-dimensional flower-like Ni-S/Co-MOF grown on Ni foam as a bifunctional electrocatalyst for efficient overall water splitting

Poor conductivity of the metal-organic frameworks (MOFs) limits their applications in overall water splitting. Surface sulfur (S) doping transition metal hydroxides would effectively improve the conductivity and adjust the electronic structure to generate additional electroactive sites. Herein, we fabricated a Ni-S/Co-MOF/NF catalyst by electroplating a Ni-S film on the 3D flower-like Co-MOF. Because the 3D flower-like structures are covered in Ni foam, the high exposure of active sites and good conductivity are obtained. Moreover, the synergistic effect between Ni-S and Co-MOF contributes to the redistribution of electrons in the catalyst, which can then optimize the catalytic performance of the material. The obtained 3D flower-like Ni-S/Co-MOF/NF demonstrates excellent activity toward both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in 1 M KOH, which only requires a low overpotential of 248 mV@10 mA cm-2 for the OER and 127 mV@10 mA cm-2 for the HER, respectively. At a current density of 10 mA cm-2, the Ni-S/Co-MOF/NF‖Ni-S/Co-MOF/NF requires a low cell voltage of 1.59 V to split overall water splitting.

2-Methylimidazole-modulated 2D Cu metal-organic framework for 5-hydroxymethylfurfural hydrodeoxygenation

Preparation of the high value-added chemical 2,5-dimethylfuran (2,5-DMF) from the biomass-derived platform molecule 5-hydroxymethylfurfural (HMF) is of great significance in the preparation of biofuels. Here, a bottom-up strategy was used to prepare a metal-organic framework (MOF) material with a two-dimensional nanosheet morphology, named CPM, in which an additive 2-methylimidazole was introduced into the hydrothermal process of Cu2+ ions and terephthalic acid. Subsequently, CPM-700 prepared by heat treatment under an inert atmosphere showed excellent catalytic performance in the reaction of HMF hydrodeoxygenation to 2,5-DMF. The materials before and after pyrogenation were characterized by PXRD, XPS, TEM, N2 adsorption and desorption and so on. It was confirmed that compared with the catalyst derived from the cubic MOF material self-assembled by Cu2+ and terephthalic acid, the morphology of 2D nanosheets was beneficial for the reaction of HMF to 2,5-DMF. Combined with the experimental data, the possible reaction path of 2,5-DMF preparation from HMF is that 2,5-dihydroxymethylfuran was formed by hydrogenation of the aldehyde group on the furan ring, and then 2,5-DMF was obtained by hydrogenolysis. This paper provides an effective route for 2D MOF-derived catalytic materials in the selective hydrogenation of HMF.

Hourglass-Type Polyoxometalate-Based Crystalline Material as an Efficient Proton-Conducting Solid Electrolyte

Proton exchange membrane fuel cells are limited because they are limited to working temperatures and are susceptible to damage by dramatic electrochemical environments such as hydrogen peroxide/radicals. It is necessary to develop new proton-conducting materials that are water-stable and can operate at high temperatures. The hourglass reduced molybdophosphate-based compound (H₂bimb)₃[Zn₃(H₆P₄Mo₆O₃₁)₂] (bimb = 1,4-bis[(1H-imidazol-1-yl)methyl]benzene) was designed and synthesized under solvothermal conditions. Single-crystal X-ray diffraction analyses demonstrated noticeably that CUST-571 was composed of an hourglass {Zn[P₄Mo₆]₂} structure, which consisted of two fully reduced half-units {P₄Mo₆}. It was found that CUST-571 possessed an excellent proton conductivity of 4.54 × 10^-3 S cm^-1 at 85 °C and 98% RH (relative humidity). In addition, CUST-571 is capable of an excellent catalytic decomposition of H₂O₂, which is beneficial to increase the life of fuel cells. On the basis of the aforementioned results, CUST-571 may be a promising proton-conducting polyoxometalate hybrid material in the future.