Covalently anchoring covalent organic framework on carbon nanotubes for highly efficient electrocatalytic CO2 reduction

Porphyrin-based covalent organic frameworks (Por-COF) nanosheets were vertically anchored on carbon nanotubes (CNT) with covalent connection for efficient electrocatalytic CO2 reduction reaction (CO2RR). The CNT not only acts as ideal carriers for the dispersion of Pro-COF but also facilitates electron transfer along porphyrin planes to immobilized metal active sites. As a result, covalently linked MWCNT-Por-COF-M (M: Co, Ni, Fe) display improved electrocatalytic CO2-to-CO activity and selectivity compared to pure Por-COF-M and MWCNT@Por-COF-M without covalent connection between two components. In particular, MWCNT-Por-COF-Co exhibits superior activity (FECO: 99.3%), higher partial current density and good durability in 0.5 M KHCO3 by H type cell, while MWCNT-Por-COF-Cu exhibits the highest CH4 faradaic efficiency of 71.2% in 1.0 M KOH by flow cell. The results of HRTEM and Auger spectrum revealed that the high performance of MWCNT-Por-COF-Cu could be attributed to the generated Copper-based nanoclusters during the electrocatalytic CO2RR process.