Decoupling Redox Hopping and Catalysis in Metal‐Organic Frameworks ‐based Electrocatalytic CO ₂ Reduction

Abstract

Traditional MOF e-CRR, constructed from catalytic linkers, manifest a kinetic bottleneck during their multi-electron activation. Decoupling catalysis and charge transport can address such issues. Here, we build two MOF/e-CRR systems, CoPc@NU-1000 and TPP(Co)@NU-1000, by installing cobalt metalated phthalocyanine and tetraphenylporphyrin electrocatalysts within the redox active NU-1000 MOF. For CoPc@NU-1000, the e-CRR responsive Co^I/0 potential is close to that of NU-1000 reduction compared to the TPP(Co)@NU-1000. Efficient charge delivery, defined by a higher diffusion (D_hop =4.1×10^-12 cm² s^-1 ) and low charge-transport resistance ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>R</mml:mi> <mml:mrow><mml:mi>C</mml:mi> <mml:mi>T</mml:mi></mml:mrow> <mml:mrow><mml:mi>M</mml:mi> <mml:mi>O</mml:mi> <mml:mi>F</mml:mi></mml:mrow> </mml:msubsup> <mml:annotation>${{R}_{{\rm C}{\rm T}}^{{\rm M}{\rm O}{\rm F}}}$</mml:annotation> </mml:semantics> </mml:math> =59.5 Ω) in CoPC@NU-1000 led FE_CO =80 %. In contrast, TPP(Co)@NU-1000 fared a poor FE_CO =24 % (D_hop =1.4×10^-12 cm² s^-1 and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>R</mml:mi> <mml:mrow><mml:mi>C</mml:mi> <mml:mi>T</mml:mi></mml:mrow> <mml:mrow><mml:mi>M</mml:mi> <mml:mi>O</mml:mi> <mml:mi>F</mml:mi></mml:mrow> </mml:msubsup> <mml:annotation>${{R}_{{\rm C}{\rm T}}^{{\rm M}{\rm O}{\rm F}}}$</mml:annotation> </mml:semantics> </mml:math> =91.4 Ω). For such a decoupling strategy, careful choice of the host framework is critical in pairing up with the underlying electrochemical properties of the catalysts to facilitate the charge delivery for its activation.