Implanting Polypyrrole in Metal-Porphyrin MOFs: Enhanced Electrocatalytic Performance for CO₂RR

Abstract

Metal–organic frameworks (MOFs) with plenty of active sites and high porosity have been considered as an excellent platform for the electroreduction of CO2, yet they are still restricted by the low conductivity or low efficiency. Herein, we insert the electron-conductive polypyrrole (PPy) molecule into the channel of MOFs through the in situ polymerization of pyrrole in the pore of MOF-545-Co to increase the electron-transfer ability of MOF-545-Co and the obtained hybrid materials present excellent electrocatalytic CO2RR performance. For example, FECO of PPy@MOF-545-Co can reach up to 98% at −0.8 V, almost 2 times higher than that of bare MOF-545-Co. The high performance might be attributed to the incorporation of PPy that can serve as electric cables in the channel of MOF to facilitate electron transfer during the CO2RR process. This attempt might provide new insights to improve the electrocatalytic performance of MOFs for CO2RR.

Electrocatalytic CO2Reduction: from Discrete Molecular Catalysts to Their Integrated Catalytic Materials

“…Aiming at mitigating the drawback, several effective strategies have been established: i) by connecting polyoxometalate nodes, acting as electron‐sponge to undergo rapid and reversible multi‐electron transfer, with metalloPors or metalloPcs as catalytically active components and linkers were constructed MOF catalysts, in which an oriented electron flow from the electron‐sponge to metal center in the linker was created to fulfill the multi‐electron transport requirements of ECR; [118] ii) by covalently linking electron donors (thieno[3,2‐b]thiophene, [114b] crown ether [119] and tetrathiafulvalene [120] ) as linker units with acceptors (metalloPors) as node units were constructed COF catalysts. And the resulting donor‐accepter heterojunctions can significantly promote the electron transfer from donor to metal center in the acceptor during ECR; [114b,119–120] iii) incorporating conductive assistants (polypyrrole, [121] metallocene [122] ) into the pores of MOF by postsynthetic modification approaches to assist in electron transport; iv) covalently connecting COF with conductive carbon materials; [123] v) direct epitaxial growth of oriented COF/MOF films onto the electrode substrates to improve electronic contacts with the electrode [6,108–109] . Albeit with these already‐developed strategies, these improvements are still far away from satisfaction and there remains lots of room for further improvement of the conductivity of reticular materials.…”

Polyoxometalate-based metal–organic complexes and their derivatives as electrocatalysts for energy conversion in aqueous systems

“…This technology enables valorization of CO 2 into useful chemicals like HCOOH, C 2 H 5 OH, C 2 H 4 and CH 4 . [78][79][80][81][82] The CO groups belonging to CO 2 molecules possess high bond energy, which leads to a larger overpotential for activating CO 2 . As a result, the CRR, a multi-proton and electron transfer (accepting 2, 4, 6, 8, or even more electrons) process, is kinetically sluggish.…”

Hydrophobic perfluoroalkane modified metal‐organic frameworks for the enhanced electrocatalytic reduction of CO2

“…In the recent years, porous crystalline metal‐organic frameworks (MOFs) constructed by metal nodes and functional ligands have attracted widespread attention in gas storage, separation, catalysis, sensors, and biomedicine, 37–45 and are considered as good candidates for CO 2 RR due to their high surface areas, large adsorption uptakes of CO 2 and abundant accessible single sites 46–51 . Nevertheless, the selectivity of the reported MOF electrocatalysts toward the CO 2 RR is still far from the commercial standards because the competitive HER is usually occurred in aqueous electrolyte.…”

“…In the recent years, porous crystalline metalorganic frameworks (MOFs) constructed by metal nodes and functional ligands have attracted widespread attention in gas storage, separation, catalysis, sensors, and biomedicine, [37][38][39][40][41][42][43][44][45] and are considered as good candidates for CO 2 RR due to their high surface areas, large adsorption uptakes of CO 2 and abundant accessible single sites. [46][47][48][49][50][51] Nevertheless, the selectivity of the reported MOF electrocatalysts toward the CO 2 RR is still far from the commercial standards because the competitive HER is usually occurred in aqueous electrolyte. It is believed that the local environment of the active centers including coordination structure and electrolyte environment, [52][53][54][55][56] plays an important role in adjusting the catalytic performances of the CO 2 RR.…”