Highly efficient and tunable catalytic addition of CO2 with epoxides over 2D Co-TCPP nanosheet at ambient condition

Abstract

A series of ultrathin (∼1.11–4.80 nm) 2D porphyrinic MOF nanosheets are developed and novel synergistic systems are conveniently constructed for the facile formation of cyclic carbonates. Using n-Bu4NBr (TBAB) as a co-catalyst, ultrathin (ca. 2.58 nm) Co-TCPP exhibited high catalytic activity for the solvent-free conversion of styrene oxide to cyclic carbonate, affording 99% yield at ambient conditions (25 °C and 1 atm CO2). A relatively low energy (19.6 kcal/mol) for the rate-determining step is required for Co-TCPP/TBAB nanosystem as calculated by DFT. Notably, utilizing amino acid ionic liquid (AAIL, [Bmim][Glu] or [Bmim][His]) as the modifier, a substrate-dependent protocol was proposed to fix CO2 with terminal epoxides or cyclohexene oxide, giving cyclic carbonates in 84–99% yields under mild conditions (solvent-free, 80 °C and 1 atm CO2). 13C NMR and UV-vis studies provided insights into the vital roles of AAIL during CO2 capture via carbamate dianion and in situ fabrication of Co-TCPP-AAIL. Moreover, DFT calculations also confirmed the AAIL-regulated substrate-dependent transformation strategy.