Synthesis of a conjugated porous Co(ii) porphyrinylene–ethynylene framework through alkyne metathesis and its catalytic activity study

Abstract

The development of efficient catalysts for the oxygen reduction reaction (ORR) is crucial for a number of emerging technologies, to counter energy and environment crises. Herein, we report an alkyne metathesis polymerization protocol to synthesize a conjugated microporous metalloporphyrin-based framework containing interconnected ORR catalytic centers. A simple composite of the framework and carbon black shows excellent ORR electrocatalytic activity and specificity through a four-electron reduction mechanism under both acidic and alkaline conditions. The pyrolysis of the catalyst, which is commonly involved in the preparation of ORR catalytic systems, is not necessary. Compared to monomeric metalloporphyrins, the framework shows enhanced ORR catalytic activity, presumably due to the porous and conjugated nature of the framework structure, which allows better exposure of the catalytically active sites, and efficient electron/mass transport. More importantly, the composite electrocatalyst exhibits superior durability and methanol tolerance over commercial Pt/C and metalloporphyrin monomers. Given the highly structural tunability of conjugated microporous polymers, it is conceivable that such a non-pyrolytic approach could enable the systematic exploration of the structure-activity relationship of organic framework-based ORR catalysts and eventually lead to the development of cost-effective replacements for Pt/C.

Well‐Defined Alkyne Metathesis Catalysts: Developments and Recent Applications

“…[159] Recently,Z hang and his co-workers reported the synthesis of ap orousc onjugated Co II -metallated porphyrinyleneethynylene framework (CoPEF)t hrough ADIMET,w hich was the first example of aredoxactive organic framework prepared by alkyne metathesis. [163] The Co II porphyrin monomers were polymerized by triphenolsilane bearing molybdenuma lkylidyne complex 30 in the presence of molecular sieves as 2butyne scavenger.T he framework selectively reduced O 2 to H 2 Oi nacatalytic 4-electron pathway. [163]…”

Natural Hematite as a Low-Cost and Earth-Abundant Cathode Material for Performance Improvement of Microbial Fuel Cells

“…Promising results in terms of oxygen reduction reaction activity were non-precious metals linked with organics N 4 -chelating ligands and their polymeric derivatives [7][8][9][10], such as metals tetramethoxyphenylporphyrin (TMPP), CoTMPP, FeCoTMPP, ClFeTMPP, and metals phthalocyanine (Pc), FePc, CoPc, CoNPc, FeCuPc, etc. [11][12][13][14][15][16][17]. Although these catalysts have excellent performance, all of these materials should be prepared at a high temperature with inert atmosphere [8,[11][12][13], which makes the preparation more complicated and requires an extra cost.…”

Microporous Solids En Route to Heterogeneous Electrocatalysis: The Oxygen Reduction Reaction

“…Nevertheless, the porosity was maintained around 1.3 nm and the presence of nitrogen and sulfur was still evident in NS‐Gs, which would account for the electrocatalytic activity as a result of nitrogen and sulfur modulating the spin density and charge distribution of carbon lattices, thus creating more active sites. In a different setting, a semi‐crystalline Co(II)porphyrin‐containing CMP was synthesized via alkyne metathesis, which was then mixed with carbon black to enhance the conductivity . This conjugated framework exhibited excellent ORR activity in both alkaline (0.1 m KOH) and acidic (0.5 m H 2 SO 4 ) media (−0.14 and 0.42 V vs Ag/AgCl, respectively) with a more positive onset potential when compared with the isolated metalloporphyrin monomer (−0.10 and 0.38 V vs Ag/AgCl, respectively).…”