Four Metalloporphyrinic Frameworks as Heterogeneous Catalysts for Selective Oxidation and Aldol Reaction

Heterogeneous catalytic properties of unprecedented μ-O-[FeTCPP]2 dimers (H2TCPP = meso-tetra(4-carboxyphenyl)porphyrin): an unusual superhyperfine EPR structure

Solvent accessible volume of the active catalyst μ-O-[FeTCPP]₂·nDMF dimer revealing an unusual superhyperfine EPR structure.

Porous metal-organic frameworks for heterogeneous biomimetic catalysis

Metalloporphyrins are the active sites in monooxygenases that oxidize a variety of substrates efficiently and under mild conditions. Researchers have developed artificial metalloporphyrins, but these structures have had limited catalytic applications. Homogeneous artificial metalloporphyrins can undergo catalytic deactivation via suicidal self-oxidation, which lowers their catalytic activity and sustainability relative to their counterparts in Nature. Heme molecules in protein scaffolds can maintain high efficiency over numerous catalytic cycles. Therefore, we wondered if immobilizing metalloporphyrin moieties within porous metal-organic frameworks (MOFs) could stabilize these structures and facilitate the molecular recognition of substrates and produce highly efficient biomimetic catalysis. In this Account, we describe our research to develop multifunctional porphyrinic frameworks as highly efficient heterogeneous biomimetic catalysts. Our studies indicate that porous porphyrinic frameworks provide an excellent platform for mimicking the activity of biocatalysts and developing new heterogeneous catalysts that effect new chemical transformations under mild conditions. The porous structures and framework topologies of the porphyrinic frameworks depend on the configurations, coordination donors, and porphyrin metal ions of the metalloporphyrin moieties. To improve the activity of porous porphyrinic frameworks, we have developed a two-step synthesis that introduces the functional polyoxometalates (POMs) into POM-porphyrin hybrid materials. To tune the pore structures and the catalytic properties of porphyrinic frameworks, we have designed metalloporphyrin M-H8OCPP ligands with four m-benzenedicarboxylate moieties, and introduced the secondary auxiliary ligands. The porphyrin metal ions and the secondary functional moieties that are incorporated into porous metal-organic frameworks greatly influence the catalytic properties and activities of porphyrinic frameworks in different reactions, such as the oxidation of alkylbenzenes, olefins, and hexane and the photo-oxygenation of 1,5-dihydroxynaphthalene and sulfides. The porphyrin metal ions and the secondary auxiliary sites in the pores can work together synergistically to enhance the catalytic activities of porphyrinic frameworks. Compared with their homogeneous counterparts, the activities and stabilities of the heterogeneous porphyrinic frameworks are remarkable: the immobilization of metalloporphyrins onto the pore surfaces of MOFs not only prevents their suicidal self-oxidation but also allows them to activate inert substrate molecules, such as cyclohexane. Moreover, because the bulky molecules cannot easily access the active sites inside the pores of porphyrinic frameworks, these porous materials demonstrate interesting size-selective catalytic properties toward substrates.

The effects of halogen bonding and molecular design on the self-assembly of coordination polymers of Mn(iii)-tetraarylporphyrin with axial bridging ligands

Two new coordination polymers of Mn(iii)-tetra(iodophenyl)porphyrin with isonicotinate and pyrimidine-5-carboxylate linkers have been synthesized. The effect of halogen-bonding interactions on their self-assembly in the crystalline bulk and on a graphite surface has been discussed.

Applications of metal–organic frameworks in heterogeneous supramolecular catalysis

The contributions of MOFs to the field of heterogeneous supramolecular catalysis are comprehensively reviewed with regard to active sites, selectivity, as well as host–guest chemistry.

A new strategy to construct metal–organic frameworks with ultrahigh chemical stability

A novel 2D MOF constructed from Fe³⁺and an imidazoyl base porphyrin ligand, using a new strategy, has ultra-high stability and can remain in saturated (~27.5 M) NaOH solution for a week.

Rational construction of metal–organic frameworks for heterogeneous catalysis

The recently developed strategies on designed synthesis of porous metal–organic framework catalysts and their interesting catalytic properties are summarized in this short review.

CO2 selective 1D double chain dipyridyl-porphyrin based porous coordination polymers

Two CO₂ selective 1D double chain dipyridyl-porphyrin-based porous coordination polymers, Co₃(DPyP)₃·4DMF (I) and Zn₃(DPyP)₃·2DMF·4H₂O (II) are prepared from thermal reactions of MnCl(DPyP) with Co^II and Zn^II ions in DMF.

Chemical reactions catalyzed by metalloporphyrin-based metal-organic frameworks

The synthetic versatility and the potential application of metalloporphyrins (MP) in different fields have aroused researchers' interest in studying these complexes, in an attempt to mimic biological systems such as cytochrome P-450. Over the last 40 years, synthetic MPs have been mainly used as catalysts for homogeneous or heterogeneous chemical reactions. To employ them in heterogeneous catalysis, chemists have prepared new MP-based solids by immobilizing MP onto rigid inorganic supports, a strategy that affords hybrid inorganic-organic materials. More recently, materials obtained by supramolecular assembly processes and containing MPs as building blocks have been applied in a variety of areas, like gas storage, photonic devices, separation, molecular sensing, magnets, and heterogeneous catalysis, among others. These coordination polymers, known as metal-organic frameworks (MOFs), contain organic ligands or complexes connected by metal ions or clusters, which give rise to a 1-, 2- or 3-D network. These kinds of materials presents large surface areas, Brønsted or redox sites, and high porosity, all of which are desirable features in catalysts with potential use in heterogeneous phases. Building MOFs based on MP is a good way to obtain solid catalysts that offer the advantages of bioinspired systems and zeolitic materials. In this mini review, we will adopt a historical approach to present the most relevant MP-based MOFs applicable to catalytic reactions such as oxidation, reduction, insertion of functional groups, and exchange of organic functions.