Prospects for Nanoporous Metal-Organic Materials in Advanced Separations Processes

New materials spur new technologies. Nanoporous metalorganic materials — “soft materials”analogues of zeolites, but with all of the chemical diversity of carbon compounds — may be compelling examples of this path from materials to technologies. Research teams investigating this new class of materials are trying to develop adsorbents and membranes that will revolutionize small-molecule separations, as well as new kinds of catalysts that behave as powerful arrays of artificial enzymes. In addition, metal-organic materials hold promise to act as ultra-low-density sponges that can store and release extraordinary amounts of molecular hydrogen for next-generation vehicles. Driving these materials discoveries are advances in supramolecular coordination chemistry and metal-based directedassembly chemistry. These tools are enabling scientists and engineers around the world to construct imaginative new metalorganic materials in synthetically predictable ways. This article describes some of these materials and results to date that suggest their potential for performing, among other things, demanding chemical separations. Comprising the new materials are ones based on extended porous crystalline lattices, as well as others based on aggregates of individual hollow molecules. Each type appears to offer advantages for specific applications. What they have in common, however, are good permeability, high void volumes, and well defined tailorable cavities of uniform size — precisely the properties needed for catalysis, separations, and storage/release applications. This is still an emerging field, with many opportunities; numerous new materials are being made and the potential appears great, but the performance of metal-organic materials in industrially important technologies is still a mostly unexplored frontier. The New Materials: What They Are and What They Are Already Good For