# Metal-Organic Frameworks Toward Electrocatalytic Applications
## 5 Conclusions and Outlook  
In summary, utilizing MOFs and relevant materials for various electrocatalytic purposes has become an emerging subfield in the past five years. As a catalog of highly porous supports with interconnected pore structures and tunable intra-framework functionality, MOFs can provide an ultrahigh density of accessible active sites and thus are attractive for catalysis. The findings of redox hopping behavior in MOFs opened up the feasibility to utilize MOFs for electrochemical applications,  
Figure 8: (**a**) The use of metal–organic framework (MOF)-525 thin film for electrochemical nitrite sensing [43]. Reproduced with permission from [43], Copyright Elsevier, 2015. (**b**) The design of nanocomposites composed of MOF-525 nanocrystals interconnected by graphene nanoribbons to improve the electrochemical sensing performance [137]. Reproduced with permission from [137], Copyright The Royal Society of Chemistry, 2016.  
and the rapid growth in the numbers of electrically conductive MOFs and water-stable MOFs provides more opportunity for MOFs to be served as novel electrocatalysts.  
Although to date there are already several examples of electrochemically addressable MOFs that have been utilized in hydrogen evolution, oxygen evolution, oxygen reduction, CO\({}_{2}\) reduction, and amperometric sensing, the corresponding electrochemical performances are in general quite limited; the slow redox hopping or low electrical conductivity still makes MOFs quite far away from state-of-the-art electrocatalysts in most of the cases. MOF-derived materials, either obtained by pyrolysis or in-situ electrochemical transformation, usually perform better for electrocatalytic applications compared to the crystalline MOFs at the current stage. However, most of the MOF-derived materials lose the tunable chemical functionality and the regular and interconnected porosity given by the parent MOFs. To keep these benefits provided by MOFs and further improve the corresponding electrocatalytic performance, the charge-transport rate within the MOF-based thin films must be improved. One of the strategies is to design electrically conductive MOFs possessing high porosity and water stability. As the thickness of the electrocatalytic thin film deposited on the conducting substrate is usually in the range of a few hundred nanometers to a few micrometers, extremely high electrical conductivity may not be necessary to achieve a negligible overpotential originated from the resistance of the electrocatalyst. Another alternative approach is designing the nanocomposites to integrate the advantages from different materials. The advantages of MOFs are still preserved, but another conducting material, such as nanocarbons or conducting polymers, can be incorporated with MOF crystals to facilitate charge transport within the electrocatalystally active thin film. Further research efforts are still needed to design better MOF-based materials for achieving benchmarking electrocatalytic performance in practice.  
This work was funded by the Ministry of Science and Technology (MOST) of Taiwan, under project MOST 107-2218-E-006-054-MY3. This work was also, in part, supported by the Headquarters of University Advancement at the National Cheng Kung University sponsored by the Ministry of Education (MOE) of Taiwan. We also thank the support from the Yushan Young Scholar Program under MOE, Taiwan.  
The authors declare no conflict of interest.