Recent progress in the synthesis and applications of zeolitic imidazolate framework materials is presented in this review.

Exploring highly-efficient and low-cost bifunctional electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reactions (OER) in the renewable energy area has gained its momentum but still remains a significant challenge. Here we represent a simple but efficient way that utilizes ZIF-67 as the precursor and template for the one-step generation of homogeneous dispersed cobalt sulfide/N,S-codoped porous carbon nanocomposites as high-performance electrocatalysts. Due to the favourable molecular-like structural features and uniform dispersed active sites in the precursor, the resulting nanocomposites featured with unique core-shell structure, high porosity, homogeneous dispersion active components together with N and S-doping effect, not only show excellent electrocatalytic activity towards ORR with the high onset potential (around -0.04 V vs -0.02 V for benchmark Pt/C catalyst) and four-electron pathway, and OER with a small overpotential of 0.47 V for 10 mA cm −2 current density, but also exhibit superior stability (92%) to commercial Pt/C catalyst (74%) in ORR and promising OER stability (80%) with good methanol tolerance. Our findings suggest that the transition metal sulfide-porous carbon nanocomposites derived from the one-step simultaneously sulfurization and carbonization of zeolitic imidazolate frameworks are excellent alternative bifuncitonal electrocatalysts towards ORR and OER in the next generation of energy storage and conversion technologies.With the depletion of hydrocarbon-based energy resources and the increasing global energy demands, it is imperative to develop green and sustainable energy storage and conversion technologies as alternatives to currently widely used fossil fuels. 1-3 Electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) play key roles in several important next-generation energy storage and conversion technologies, such as fuel cells, metal-air batteries and water splitting. [4][5][6][7][8][9][10][11][12][13] Hitherto, most efficient electrocatalysts for ORR/OER contain precious metals including Pt or Ir; however, due to the prohibitive cost, poor stability of precious metals, the sluggish kinetics for ORR and the large polarisation, it is highly desirable to discover highly efficient and low-cost earthabundant non-precious electroactive materials that can rival the performances of precious metal-based catalysts. 14-17Many efforts have, therefore, been devoted to transition metal oxides/sulfides based materials, as many transition metals like cobalt, manganese have been widely considered to be electrochemical active for ORR and OER. Particularly, cobalt sulfides (Co x S y ) with different phases have been previously investigated as ORR and OER electrode catalysts and exhibited attractive electrocatalytic performance among different nonprecious and late transition metal chalcogenides.18 Co 9 S 8 is a good catalyst for ORR. 21 However, the complicated preparation procedures coupled with the low electrical conductivities of cobalt s...

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• Doping and porosity generation were completed simultaneously. • Metal-heteroatom-doped carbon nanofibers are flexible, porous, and well dispersed. • Results include excellent oxygen reduction reaction and enhanced Zn-air battery performance.

A series of nanocomposites of cobalt embedded in N-doped nanoporous carbons, carbon nanotubes or hollow carbon onions have been synthesized by a one-step carbonization of metal-organic-framework ZIF-67. The effect of the carbonization temperature on the structural evolution of the resulting nanocomposites has been investigated in detail. Among the as-synthesized materials, the cobalt/nanoporous N-doped carbon composites have demonstrated excellent electrocatalytic activities and durability towards oxygen reduction reaction in alkaline medium. Compared to the benchmark Pt/C catalyst, the optimized Co@C-800 (carbonized at 800 °C) exhibited high oxygen reduction reaction activity with an onset potential of 0.92 V, and a half-wave potential of 0.82 V. Moreover, the optimized Co@C-800 also showed enhanced electrocatalytic activity towards oxygen evolution reaction from water splitting, with a low onset potential of 1.43 V and a potential of 1.61 V at 10 mA cm−2 current density. This work offered a simple solution to develop metal-organic-framework-derived materials for highly efficient electrochemical applications.