Energy Band Alignment and Redox‐Active Sites in Metalloporphyrin‐Spaced Metal‐Catechol Frameworks for Enhanced CO₂ Photoreduction

Abstract

Twon ew chemically stable metalloporphyrinbridged metal-catechol frameworks,I nTCP-Co and FeTCP-Co,w ere constructed to achieve artificial photosynthesis without additional sacrificial agents and photosensitizers.T he CO 2 photoreduction rate over FeTCP-Co considerably exceeds that obtained over InTCP-Co,a nd the incorporation of uncoordinated hydroxyl groups,associated with catechol,into the network further promotes the photocatalytic activity.T he iron-oxocoordination chain assists energy band alignment and provides ar edox-active site,a nd the uncoordinated hydroxyl group contributes to the visible-light absorptance,c hargecarrier transfer,a nd CO 2 -scaffold affinity.W ith af ormic acid selectivity of 97.8 %, FeTCP-OH-Co affords CO 2 photoconversion with areaction rate 4.3 and 15.7 times higher than those of FeTCP-Co and InTCP-Co,respectively.These findings are also consistent with the spectroscopic study and DFT calculation.

Expanding the horizons of porphyrin metal–organic frameworks via catecholate coordination: exploring structural diversity, material stability and redox properties

“…More importantly, the choice of the formamide again has a profound effect on the crystallized phase. While DMF leads exclusively to the formation of phase 1 (in agreement with recent reports 83,84 ), its replacement by DEF promotes the formation of phase 2 (CatP-MOF-2) based on a very different inorganic SBU and with larger pores (see below). Overall, this difference in reactivity observed for all the metals in DEF is tentatively attributed to a templating effect of the solvent and/or the presence of a small amount of dimethylamine, which can form helicoidal supramolecular assemblies 92 promoting the formation of MOFs with larger pores.…”

“…This result differs from previous ndings from Chen et al, showing Co-CatPMOF-1(Fe) to be stable in water from pH = 4 to 11. 83 Hence, at least in our hands and in contrast to the initial expectations, porphyrin based M 3+ -catecholate MOFs present a moderate stability. The benet associated with phenolic ligands eventually is far more pronounced when moving to M(IV) and gallate ligands, 2,51 likely because of the increased charge of both components leading to stronger metal-ligand connections.…”

“…Hence, the three compounds present a moderate thermal stability in air, significantly lower than that of standard porphyrin carboxylate MOFs. This behavior, which was already observed in other phenolatebased MOFs, 50,70,83,107,108 likely relates to the easier oxidation of the ligand. This is supported by the fact that the three solids present a signicantly higher thermal stability under nitrogen: as shown Fig.…”

Enabling heterogeneous catalysis to achieve carbon neutrality: Directional catalytic conversion of CO2 into carboxylic acids

“…In addition, some cheap and efficient heterogeneous catalysts such as alpha-iron oxyhydroxide/Al 2 O 3 , nonporous Pb-containing polymers (CPs), metalloporphyrin based metal-catechol frameworks (MCFs) and dual Ti 6 Cu 3 clusters based polymers have been developed to achieve high formic acid yields with the appealing properties such as high visible-light adsorption, fast charge separation, and transfer efficiency. [51][52][53][54] Typically, the organic units in these catalysts contribute to light adsorption, and the metal sites play as the catalytic sites to promote CO 2 conversion.…”

“…For instance, an enzyme, formate dehydrogenase (FDH), is introduced into the olefin‐linked COFs to form the photocatalyst due to its high activity and selectivity for formic acid formation, 50 although the high cost of large‐scale synthesis of FDH via microbial expression limits its wide application. In addition, some cheap and efficient heterogeneous catalysts such as alpha‐iron oxyhydroxide/Al 2 O 3 , nonporous Pb‐containing polymers (CPs), metalloporphyrin based metal‐catechol frameworks (MCFs) and dual Ti 6 Cu 3 clusters based polymers have been developed to achieve high formic acid yields with the appealing properties such as high visible‐light adsorption, fast charge separation, and transfer efficiency 51–54 . Typically, the organic units in these catalysts contribute to light adsorption, and the metal sites play as the catalytic sites to promote CO 2 conversion.…”