This Review focuses on research oriented toward elucidation of the various aspects that determine adsorption of CO in metal-organic frameworks and its separation from gas mixtures found in industrial processes. It includes theoretical, experimental, and combined approaches able to characterize the materials, investigate the adsorption/desorption/reaction properties of the adsorbates inside such environments, screen and design new materials, and analyze additional factors such as material regenerability, stability, effects of impurities, and cost among several factors that influence the effectiveness of the separations. CO adsorption, separations, and membranes are reviewed followed by an analysis of the effects of stability, impurities, and process operation conditions on practical applications.

Density functional theory calculations are performed to explain the electrical behavior of a π-conjugated oligo(phenylene ethynylene) resembling a resonant tunneling diode. Results of this theoretical study are compatible with the assumptions that electron transport occurs through the lowest unoccupied molecular orbital, that the conduction barrier is determined by the molecule chemical potential, and that the molecule becomes charged as the external potential increases. We are able to explain the nonlinear character of the current-voltage characteristic of the molecule and its temperature dependence. The intrinsic controlledamplification feature of these molecules is indicated.

Green function and density functional theories are used to study electron transport characteristics through single molecules addressed by two metallic contacts. Each contact is modeled with one nanoscopic end connected to the molecule and one macroscopic end connected to an external potential difference. The method can be applied to any molecular system for which ab initio calculations can be performed. It allows us to determine the molecular orbitals participating in the electron-transfer process, the current-voltage characteristics of the junction, the density of states, and the transmission function, among other properties, providing a fundamental tool for the development of molecular electronics. The method is tested with Au n -S-(p-C 6 H 4 )-S-Au n (n ) 1-5) connected to bulk gold. Current-voltage characteristics are in excellent agreement with a break junction experiment and with other ab initio calculations, yielding new insights regarding electron transport through single molecules.