A thin film of a metalloporphyrin metal-organic framework consisting of [5,10,15,20-(4-carboxyphenyl)porphyrin]Co(III) (CoTCPP) struts bound by linear trinuclear Co(II)-carboxylate clusters has been prepared solvothermally on conductive fluorine-doped tin oxide substrates. Characterization of this mesoporous thin film material, designated as CoPIZA/FTO, which is equipped with large cavities and access to metal active sites, reveals an electrochemically active material. Cyclic voltammetry displays a reversible peak with E(1/2) at -1.04 V vs ferrocyanide attributed to the (Co(III/II)TCPP)CoPIZA redox couple and a quasi-reversible peak at -1.45 V vs ferrocyanide, which corresponds to the reduction of (Co(II/I)TCPP)CoPIZA. Analysis of the spectroelectrochemical response for the (Co(II/I)TCPP)CoPIZA redox couple revealed non-Nernstian reduction with a nonideality factor of 2 and an E(1/2) of -1.39 V vs ferrocyanide. The film was shown to retain its structural integrity with applied potential, as was demonstrated spectroelectrochemically with maintenance of isosbestic points at 430, 458, and 544 nm corresponding to the (Co(III/II)TCPP)CoPIZA transition and at 390 and 449 nm corresponding to the (Co(II/I)TCPP)CoPIZA transition. The mechanism of charge transport through the film is proposed to be a redox hopping mechanism, which is supported by both cyclic voltammetry and spectroelectrochemistry. A fit of the time-dependent spectroelectrochemical data to a modified Cottrell equation gave an apparent diffusion coefficient of 7.55 (±0.05) × 10(-14) cm(2)/s for ambipolar electron and cation transport throughout the film. Upon reduction of the metalloporphyrin struts to (Co(I)TCPP)CoPIZA, the CoPIZA thin film demonstrated catalytic activity for the reduction of carbon tetrachloride.

What was the inspiration for this cover design? The catalyst-modified MOF thin filmi sg rown on al eaf-like electrode conductive substrate. The "leaf" electrochemically oxidizesw ater,o ne of the half reactions required for natural photosynthesis.

A highly robust metal-organic framework (MOF) constructed from Zr oxo clusters and Fe(III) porphyrin linkers, PCN-223-Fe was investigated as a heterogeneous catalyst for oxygen reduction reaction (ORR). Films of the framework were grown on a conductive FTO substrate and showed a high catalytic current upon application of cathodic potentials and achieved high HO/HO selectivity. In addition, the effect of the proton source on the catalytic performance was also investigated.

Ruthenium(ii) polypyridyl-doped metal–organic framework sensitized films on TiO2 for photovoltaics reveal that the preparative method of dye doping/incorporation into the MOF is integral to the total solar cell efficiency.

The chronoamperometric response (I vs t) of three metallocene-doped metal–organic frameworks (MOFs) thin films (M-NU-1000, M = Fe, Ru, Os) in two different electrolytes (tetrabutyl­ammonium hexafluoro­phosphate [TBAPF6] and tetrabutylammonium tetrakis­(pentafluorophenyl)­borate [TBATFAB]) was utilized to elucidate the diffusion coefficients of electrons and ions (D e and D i, respectively) through the structure in response to an oxidizing applied bias. The application of a theoretical model for solid state voltammetry to the experimental data revealed that the diffusion of ions is the rate-determining step at the three different time stages of the electrochemical transformation: an initial stage characterized by rapid electron diffusion along the crystal-solution boundary (stage A), a second stage that represents the diffusion of electrons and ions into the bulk of the MOF crystallite (stage B), and a final period of the conversion dominated only by the diffusion of ions (stage C). Remarkably, electron diffusion (D e) increased in the order of Fe < Ru < Os using PF6 1– as the counteranion in all the stages of the voltammogram, demonstrating the strategy to modulate the rate of electron transport through the incorporation of rapidly self-exchanging molecular moieties into the MOF structure. The D e values obtained with larger TFAB1– counteranion were generally in agreement with the previous trend but were on average lower than those obtained with PF6 1–. Similarly, the ion diffusion coefficient (D i) was generally higher for TFAB1– than for PF6 1– as the ions diffuse into the crystal bulk, due to the high degree of ion-pair association between PF6 1– and the metallocenium ion, resulting in a faster penetration of the weakly associated TFAB1– anion through the MOF pores. These structure–function relationships provide a foundation for the future design, control, and optimization of electron and ion transport properties in MOF thin films.