Supercritical processing as a route to high internal surface areas and permanent microporosity in metal-organic framework materials.

Careful processing of four representative metal-organic framework (MOF) materials with liquid and supercritical carbon dioxide (ScD) leads to substantial, or in some cases spectacular (up to 1200%), increases in gas-accessible surface area. Maximization of surface area is key to the optimization of MOFs for many potential applications. Preliminary evidence points to inhibition of mesopore collapse, and therefore micropore accessibility, as the basis for the extraordinarily efficacious outcome of ScD-based activation.

Liquid/liquid interface polymerized porphyrin membranes displaying size-selective molecular and ionic permeability.

Thin polymeric membranes have been formed by liquid/liquid interfacial copolymerization of a sterically demanding tetraphenylporphyrin derivative having reactive phenol substituents and a second porphyrin having reactive acid chloride groups. The out-of-plane steric demand is created by 3,5-hexoxyphenyl groups positioned at two of the four meso carbons of the porphyrin ring. The bulky substituents were designed to create local pockets and extended pores within the resulting ester-linked copolymer.

Differential substituent effects of beta-halogens in water-soluble porphyrins.

The first water-soluble beta-octafluorinated porphyrins, 5,10,15,20-tetrakis(4-sulfonatophenyl)-2,3,7,8,12,13,17,18- octafluoroporphyrin, 1, and 5,10,15,20-tetrakis(2,6-difluoro-3-sulfonatophenyl)-2,3,7,8,12,13,17,18- octafluoroporphyrin, 2, have been prepared and their aqueous aggregation, acid-base, and optical properties have been characterized. The porphyrins are tetraanionic at neutral pH (at pH = 3-11 for 1 and pH = 0-9 for 2). Semiempirical (AM1) calculations provide evidence that somewhat unusual acidity characteristics of the fluorinated compounds (with respect to similar brominated porphyrins) can be rationalized solely on the basis of chemical hardness and electronegativity arguments.

Reversible electrochemical generation of a rhodium(II) porphyrin: thwarting disproportionation with weakly coordinating anions.

We report electrochemical generation of a stable Rh(II) porphyrin (Rh(II)(F(28)TPP)) from a four-coordinate Rh(I) precursor [Rh(I)(F(28)TPP)](-) dissolved in weakly coordinating electrolyte solutions. This work provides the first example of an unambiguously reversible one-electron electrochemical oxidation of a Rh(I)(por), and demonstrates that electrochemical oxidation can be performed under conditions that are compatible with alkane activation. These studies begin to classify those media capable of supporting a stable Rh(II)(por), and those that induce disproportionation.