Switchable Water: Microfluidic Investigation of Liquid–Liquid Phase Separation Mediated by Carbon Dioxide

Increase in the ionic strength of water that is mediated by the reaction of carbon dioxide (CO₂) with nitrogenous bases is a promising approach toward phase separation in mixtures of water with organic solvents and potentially water purification. Conventional macroscale studies of this complicated process are challenging, due to its occurrence via several consecutive and concurrent steps, mass transfer limitation, and lack of control over gas–liquid interfaces. We report a new microfluidic strategy for fundamental studies of liquid–liquid phase separation mediated by CO₂ as well as screening of the efficiency of nitrogenous agents. A single set of microfluidic experiments provided qualitative and quantitative information on the kinetics and completeness of water–tetrahydrofuran phase separation, the minimum amount of CO₂ required to complete phase separation, the total CO₂ uptake, and the rate of CO₂ consumption by the liquid mixture. The efficiency of tertiary diamines with different lengths of alkyl chain was examined in a time- and labor-efficient manner and characterized with the proposed efficiency parameter. A wealth of information obtained using the MF methodology can facilitate the development of new additives for switchable solvents in green chemistry applications

Metal-Free Catalytic Hydrogenation of Polar Substrates by Frustrated Lewis Pairs

In 2006, our group reported the first metal-free systems that reversibly activate hydrogen. This finding was extended to the discovery of “frustrated Lewis pair” (FLP) catalysts for hydrogenation. It is this catalysis that is the focal point of this article. The development and applications of such FLP hydrogenation catalysts are reviewed, and some previously unpublished data are reported. The scope of the substrates is expanded. Optimal conditions and functional group tolerance are considered and applied to targets of potential commercial significance. Recent developments in asymmetric FLP hydrogenations are also reviewed. The future of FLP hydrogenation catalysts is considered