Colorimetric switching and sensing of CO2 based on reversible proton movement between the two heavy atoms in low barrier hydrogen bond in PDI radical anion/b-PEI hydrogen bonding complex

The photophysical properties of the hydrogen bond complexes consisting of low-barrier hydrogen bond (LBHB) depend on their environmental condition. However, the stimuli responsive materials based on LBHB are still a challenging problem. Here, we report a novel material system which has high color response to CO 2 based on the position changes of the proton between the two heavy atoms in the low barrier hydrogen bond. Perylene diimide radical anion/branched polyethyleneimine hydrogen bonding complex (TFPDI-b-PEI) linked by low-barrier hydrogen bond ([O 1 -----H 1 ---N 1 ] −1 ) is obtained and it shows the maximum absorption of 789 nm. Meanwhile, the maximum absorption of TFPDI-b-PEI appears at 561 nm with purple when CO 2 is adsorbed in the branched polyethyleneimine . In essence, the geometry of LBHB in TFPDI-b-PEI can switch between two types of hydrogen bond ([O 1 ----H 1 ----N 1 ] −1 and [O 1 -----H 1 ---N 1 ] −1 ) via adjusting the interaction between the surrounding molecule and amine groups in LBHB by interaction of CO 2 with TFPDI-b-PEI. Further the TFPDI-b-PEI shows excellent color switching and colorimetric sensing performance for CO 2 aqueous solution and its gas based on this hydrogen bond dynamic characteristic.