A solvent free synthesis was developed for FeDhaTph-COF containing 5,10,15,20-tetra-(4-aminophenyl)porphyrine Fe(III) chloride (FeTAPPCl) and 2,5-dihydroxyterephthalaldehyde (Dha) for the reduction of CO2. High resolution N1s XPS spectra of the COF revealed the formation of imine bonds and hemiaminal groups. Cyclic voltammetry of the FeDhaTph-COF electrodes revealed three redox couples,whereas the Fe(II/I) and Fe(I/0) redox couples were observed at comparable potentials as FeTAPPCl in solution. ICP-OES results suggested that the COF network has retained Fe centers substantially better than physiadsorption in either MeCN and DMF solvent. CPE studies also showed that FeDhaTph-COF electrodes have good TOF (&gt; 600 h-1 per mole of electroactive Fe sites) and reasonable Faradaic efficiency for CO (an average of 80%) at -2.2 V (vs Ag/AgCl) over three hours in MeCN with 0.5 M trifluoroethanol (TFE). The COF electrodes have higher TON and selectivity for CO in MeCN than in DMF. Post-CPE XPS analysis suggested that the imine bonds and hemianimal groups remained intact while the porphyrin network could have been degraded.

Facile solvent free synthesis of iron porphyrin COFs for CO2 reduction

2019 Fall National Meeting

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