Stable Dioxin-Linked Metallophthalocyanine Covalent Organic Frameworks (COFs) as Photo-Coupled Electrocatalysts for CO2 Reduction

In this work, we rationally designed a series of crystalline and stable dioxin-linked metallophthalocyanine covalent organic frameworks (COFs; MPc-TFPN COF, M=Ni, Co, Zn) under the guidance of reticular chemistry. As a novel single-site catalysts (SSCs), NiPc/CoPc-TFPN COF exhibited outstanding activity and selectivity for electrocatalytic CO2 reduction (ECR; Faradaic efficiency of CO (FECO)=99.8(+/- 1.24) %/ 96.1(+/- 1.25) % for NiPc/CoPc-TFPN COF). More importantly, when coupled with light, the FECO and current density (j(CO)) were further improved across the applied potential range (-0.6 to -1.2 V vs. RHE) compared to the dark environment for NiPc-TFPN COF (j(CO) increased from 14.1 to 17.5 A g(-1) at -0.9 V; FECO reached up to ca. 100 % at -0.8 to -0.9 V). Furthermore, an in-depth mechanism study was established by density functional theory (DFT) simulation and experimental characterization. For the first time, this work explored the application of COFs as photo-coupled electrocatalysts to improve ECR efficiency, which showed the potential of using light-sensitive COFs in the field of electrocatalysis.