**Acknowledgements**

introduction of MWCNT and the *in‐situ* N‐doped carbon carbonized from ligands could significantly improve the electronic conductivity of the catalysts. Thus, better OERactivity was observed with an onset potential of only 1.5 V (vs. RHE). Ma et al. [64] synthesized MOF‐ derived Co3O4‐carbon porous nanowire arrays. The Co3O4‐carbon were directly prepared on Cu foil as a working electrode. Since this electrode is binder‐free and carbon is formed *in situ*, the charge conductivity performance is greatly improved, resulting in excellent OER catalyt‐ ic activity in 0.1 M KOH solution. It shows a sharp onset potential of 1.47 V (vs. RHE), very close to that of IrO2/C (1.45 V vs. RHE). The durability is also an important criterion for OER catalysts. The chronopotentiometric response at a current density of 10 mA·cm−2 was also recorded, and only 6.5% attenuation was observed within 30 h on Co3O4‐carbon, while that of

The above results demonstrate that MOFs‐derived catalysts show much enhanced OER catalytic performance than pristine MOFs. There are likely several reasons for that. On one hand, carbon materials formed *in situ* or *ex situ* in catalysts can promote electronic conductiv‐ ity and accelerate charge transfer. On the other hand, the OER active species can be well‐ dispersed on carbon materials, resulting in improved OER activity. In addition, the strong interactions between OER active species and carbon materials stabilize the OER active site

MOFs‐based electrocatalysts for HER and/or OER are rapidly developed in recent years due to unique structures of MOFs. These catalysts mainly include MOFs catalysts, MOFs sup‐ ports for catalysts, and MOFs‐derived catalysts. Due to the fact that the pore structures and functions are tunable and devisable, it is convenient to directly design and construct the active sites for HER and/or OER in MOFs during the synthesis process. However, the vast majority of the synthesized MOFs suffer from poor electronic conductivity, leading to low electron transfer efficiency, which restricts catalytic performance. MOFs are highly porous materials and have ultrahigh specific surface area, thus they are regarded as the most promising support materials for catalysts. The active species for HER or OER can be well dispersed at the surfaces of MOFs or embedded in MOFs matrix, resulting in improved catalytic performance for HER or OER. However, MOFs are microporous materials with small aperture size (<2 nm).On one hand, the active species are difficult to be introduced in their pore channels. Hence, one cannot obtain the catalysts with high activity and stability for HER or OER. On the other hand, the accommodation of electrolyte in the pore channels is very limited. Thus, the active centers in MOFs cannot access the electrolytes with high efficiency. In addition, the poor electronic conductivity of MOFs is another drawback of these catalysts. Some post‐treatment methods can greatly improve the electrical conductivity of MOFs‐derived catalysts. However, the collapse of the pore structures of MOFs usually occurs during the preparation of the MOFs‐ derived catalysts leading to a decreased specific surface area of the catalysts, which is adverse to the development of MOFs‐derived catalysts with high catalytic performance for HER or

IrO2/C is 4.7 times lager under the same condition.

**6. Conclusions**

126 128Metal-Organic Frameworks

OER.

structures, thus leading to enhanced OER activity durability.

This work is supported by the National Natural Science Foundation of China (Project No. 21276018), the Natural Science Foundation of Jiangsu Province of China (Project No. BK20140268), the Fundamental Research Funds for the Central Universities (Project No. buctrc201526), and the Changzhou Sci&Tech Program (Project No. CJ20159006).
