Quantifying the efficiency of CO2 capture by Lewis pairs

Abstract

A microfluidic strategy has been used for the time- and labour-efficient evaluation of the relative efficiency and thermodynamic parameters of CO₂ binding by three Lewis acid/base combinations, where efficiency is based on the amount of CO₂ taken up per binding unit in solution. Neither tBu₃P nor B(C₆F₅)₃ were independently effective at CO₂ capture, and the combination of the imidazolin-2-ylidenamino-substituted phosphine (NIiPr)₃P and B(C₆F₅)₃ was equally ineffective. Nonetheless, an archetypal frustrated Lewis pair (FLP) comprised of tBu₃P and B(C₆F₅)₃ was shown to bind CO₂ more efficiently than either the FLP derived from tetramethylpiperidine (TMP) and B(C₆F₅)₃ or the highly basic phosphine (NIiPr)₃P. Moreover, the proposed microfluidic platform was used to elucidate the thermodynamic parameters for these reactions.