Development of high capacity moisture-swing DAC sorbent for direct air capture of CO2

•CO2 capacity in DAC sorbents was significantly enhanced by employing the double quaternary ammonium strategy.•Diamine-DQ-AER exhibits CO2 capacity of ∼3.41 mmol/g under moisture swing DAC conditions.•The 6-cycle test demonstrated stable performance with DAC capacity 3 times that reported in the literature.•A complete desorption kinetic curve reveals a 2-stage process where CO2 release more efficiently in the 1st stage.•Results provide practical information for DAC process design, optimization, and industrial implementation.