Co phthalocyanine covalent organic frameworks with enhanced π-electron delocalization for boosted electrocatalytic CO₂ reduction reaction

By connecting Co phthalocyanine with 1,2,4,5-benzenetetramine (BTM) or 3,3'-diaminobenzidine (DAB), two covalent organic frameworks (CoPc-BTM-COF and CoPc-DAB-COF) with tuned π-delocalization features were synthesized for electrocatalytic CO₂ reduction. CoPc-BTM-COF is more active than its DAB-linked counterpart, displaying a 2-fold larger partial current density for CO production (-24.2 <i>versus</i> -12.1 mA cm^-2) at -1.0 V <i>versus</i> the RHE. We propose that this enhancement is due to the extended π-conjugation in the BTM-linked COF, which (1) improves bulk conductivity (1.0 <i>versus</i> 0.3 mS cm^-1) and (2) reduces charge transfer resistance by 40%.