Nanoporous molecular crystals

Nanoporous Molecular Crystals (NMCs) are nanoporous materials composed of discrete molecules between which there are only non-covalent interactions—i.e. they do not possess an extended framework composed of covalent or coordination bonds. They are formed from removing guest molecules from inclusion compounds (ICs) a process that for most ICs usually results in the collapse of the open structure of the crystals but in the case of NMCs the packing of the host molecules is retained and nanoporosity obtained. In recent years a number of NMCs have been confirmed by the technique of gas adsorption and these materials are surveyed in this feature article. In addition, the reasons for stability of these crystals are discussed. It is the author's belief that many more ICs, the structures of which are readily obtainable from the Cambridge Structural Database (CSD), may act as precursors to NMCs

Polymers of intrinsic microporosity

This paper focuses on polymers that demonstrate microporosity without possessing a network of covalent bonds—the so-called polymers of intrinsic microporosity (PIM). PIMs combine solution processability and microporosity with structural diversity and have proven utility for making membranes and sensors. After a historical account of the development of PIMs, their synthesis is described along with a comprehensive review of the PIMs that have been prepared to date. The important methods of characterising intrinsic microporosity, such as gas absorption, are outlined and structure-property relationships explained. Finally, the applications of PIMs as sensors and membranes for gas and vapour separations, organic nanofiltration, and pervaporation are described

Catechin or quercetin guests in an intrinsically microporous polyamine (PIM-EA-TB) host: accumulation, reactivity, and release

Microporous polymer materials based on molecularly "stiff"structures provide intrinsic microporosity, typical micropore sizes of 0.5 nm to 1.5 nm, and the ability to bind guest species. The polyamine PIM-EA-TB contains abundant tertiary amine sites to interact via hydrogen bonding to guest species in micropores. Here, quercetin and catechin are demonstrated to bind and accumulate into PIM-EA-TB. Voltammetric data suggest apparent Langmuirian binding constants for catechin of 550 (±50) × 103 M-1 in acidic solution at pH 2 (PIM-EA-TB is protonated) and 130 (±13) × 103 M-1 in neutral solution at pH 6 (PIM-EA-TB is not protonated). The binding capacity is typically 1 : 1 (guest : host polymer repeat unit), but higher loadings are readily achieved by host/guest co-deposition from tetrahydrofuran solution. In the rigid polymer environment, bound ortho-quinol guest species exhibit 2-electron 2-proton redox transformation to the corresponding quinones, but only in a thin mono-layer film close to the electrode surface. Release of guest molecules occurs depending on the level of loading and on the type of guest either spontaneously or with electrochemical stimuli