Gas Storage in Porous Molecular Materials

Molecules with permanent porosity in the solid state have been studied for decades. Porosity in these systems is governed by intrinsic pore space, as in cages or macrocycles, and extrinsic void space, created through loose, intermolecular solid-state packing. The development of permanently porous molecular materials, especially cages with organic or metal–organic composition, has seen increased interest over the past decade, and as such, incredibly high surface areas have been reported for these solids. Despite this, examples of these materials being explored for gas storage applications are relatively limited. This minireview outlines existing molecular systems that have been investigated for gas storage and highlights strategies that have been used to understand adsorption mechanisms in porous molecular materials.     

Thermogravimetric analysis of SPEEK membranes: Thermal stability, degree of sulfonation and cross-linking reaction

Thermal degradation of SPEEK membranes is studied by coupling thermogravimetric analysis (TGA) and mass spectrometry (MS). Main mass losses can be attributed to water evaporation, desulfonation and oxidative pyrolysis of polymer main chain. The analysis can be used to determine the degree of sulfonation (DS) and the degree of cross-linking (DCL) between macromolecular chains. Furthermore, the thermogravimetric curves can be modelled using non-isothermal chemical kinetics, allowing determination of activation energies during thermal degradation of SPEEK membranes.     

Hierarchical Structure of NiMo Hydrodesulfurization Catalysts Determined by Ptychographic X‐Ray Computed Tomography

Hydrodesulphurization, the removal of sulphur from crude oils, is an essential catalytic process in the petroleum industry safeguarding the production of clean hydrocarbons. Sulphur removal is critical for the functionality of downstream processes and vital to the elimination of environmental pollutants. The effectiveness of such an endeavour is among other factors determined by the structural arrangement of the heterogeneous catalyst. Namely, the accessibility of the catalytically active molybdenum disulphide (MoS₂) slabs located on the surfaces of a porous alumina carrier. Here, we examined a series of pristine sulfided Mo and NiMo hydrodesulphurization catalysts of increasing metal loading prepared on commercial alumina carriers using ptychographic X‐ray computed nanotomography. Structural analysis revealed a build consisting of two interwoven support matrix elements differing in nanoporosity. With increasing metal loading, approaching that of industrial catalysts, these matrix elements exhibit a progressively dissimilar MoS₂ surface coverage as well as MoS₂ cluster formation at the matrix element boundaries. This is suggestive of metal deposition limitations and/ or catalyst activation and following prohibitive of optimal catalytic utilization. These results will allow for diffusivity calculations, a better rationale of current generation catalyst performance as well as a better distribution of the active phase in next‐generation hydrodesulphurization catalysts.     

An Improved Synthesis of 2,2-Dialkyl-1,3-Indanediones

2,2-Dialkyl-1,3-indanediones are useful synthetic intermediates (^1,2) and are know to possess an anticonvulsive activity (³). These compounds are usually prepared by alkylation of 1,3-indanedione under drastic conditions and thus are obtained with low yields (20% to 40%). We describe here a convenient and high yield procedure for the synthesis of symmetrical and unsymmetrical 2,2-dialkyl-1,3-in-danediones based on alkylation of 1,3-indanediones in the presence of celite coated with potassium fluoride (KF-celite). This new reagent has been very recently used to carry out various alkylation reactions (³). We found that KF-celite promotes excellent C-dialkylation (⁴) of 1,3-indanedione la, giving rise to symmetrical 2,2-dialkylated compounds 2a. In the same way, unsymmetrical 2,2-dialkyl-1,3 indanediones 2b can be easily prepared from 2-methyl-1,3-indanedione Ib (⁵).     

Backscattering suppression in supersonic 1D polariton condensates

We investigate the effect of disorder on the propagation of one-dimensional polariton condensates in semiconductor microcavities. We observe a strong suppression of the backscattering produced by the imperfections of the structure when increasing the condensate density. This suppression occurs in the supersonic regime and is simultaneous to the onset of parametric instabilities which enable the "hopping" of the condensate through the disorder. Our results evidence a new mechanism for the strong scattering reduction of polaritons at high speeds.