Sorption and catalysis by robust microporous metalloporphyrin framework solids

Abstract

ABSTRACT:Two isostructural metalloporphyrin framework solids have been synthesized. Both frameworks contains manganese(III) metal complexes of trans-dicarboxylateporphyrins whose peripheralcarboxylates coordinate the edges of tetrahedral Zn 4 O +6 clusters; the two metalloporphyrins explored are Mn(III) and Co(II). The cubic interpenetrated frameworks have 72% free volume and 4 × 7 Å averaged size pores. The evacuated frameworks are robust and retain a structure open to the sorption of substrates with medium polarity. The manganese porphyrin framework catalyzes the hydroxylation of cyclic and linear alkanes with iodosylbenzene as oxidant in a size-and polarityselective manner. In addition, the catalysis was found to occur within the pores, making this a rare case of porphyrin framework solid with interior catalysis.

The Research on Porphyrins and Analogues in Brazil: A Small Review Covering Catalytic and other Applications since the Beginning at Universidade de São Paulo in Ribeirão Preto until the Joint Venture between Brazilian Researchers and Colleagues from Universidade de Aveiro, Portugal

“…This is an important aspect, considering the hard synthetic conditions usually required 77 and the cost of the procedure (for example, 10 g of a first-generation porphyrin [H 2 (TPP)], a poor catalyst when metallated, can cost about 79 Euros, and 1 g of the second-generation [H 2 (TPFPP)] can cost 146 Euros). 78 To overcome these drawbacks, one of the alternatives that has been intensively explored by us and others in Brazil and abroad is to prepare insoluble catalytic solids based on metalloporphyrins through different strategies: (i) immobilization of the catalytic species in organic or inorganic matrices (Table 1); (ii) preparation of insoluble solids by MP heterogenization via a metalorganic frameworks (MOF) structure (metal organic framework), 80,[140][141][142][143][144][145][146] or via a microporous polymer network (e.g., POM = porous organic polymers, COF = covalent organic framework), [147][148][149][150][151][152][153][154][155][156] or by preparing polymeric organic-inorganic hybrid materials containing a MP in their structures (e.g., porphyrinic silica solids) ( Figure 4). 71,[157][158][159][160][161][162] These two main strategies (i and ii) frequently prevent MP self-destruction and in most cases facilitate the recovery and reuse of the catalyst.…”

“…In spite of all the different solids used as supports for the immobilization of metalloporphyrins (Table 1), there is an expectation that MPs organized as porous materials, either using a porous solid as support (e.g., macroporous LDH, mesoporous silicas or zeolites), [85][86][87][89][90][91]99,100,125 or integrated into porous structures, such as metal-organic frameworks (MOFs) 27,80,140,141,145,146,192,193 or porous organic polymers (e.g., PIM = polymers of intrinsic microporosity), 149,153 will have enhanced catalytic performance, mainly regarding the selectivity, relative to non-porous materials, since the confinement effect for reagents and/or products may lead to unusual and unexpected selectivities for the same reaction relative to a homogeneous environment.…”