Quantifying the efficiency of CO2 capture by Lewis pairs

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 tBu(3)P nor B(C6F5)(3) were independently effective at CO2 capture, and the combination of the imidazolin-2-ylidenamino-substituted phosphine (NIiPr)(3)P and B(C6F5)(3) was equally ineffective. Nonetheless, an archetypal frustrated Lewis pair (FLP) comprised of tBu(3)P 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)(3)P. Moreover, the proposed microfluidic platform was used to elucidate the thermodynamic parameters for these reactions.