Mg2(dobdc) crystals adhere to Matrimid matrix membranes bridged by diethylenetriamine (DETA) as an adhesion agent for efficient CO2 separation

•DETA-bridged Mg2(dobdc) crystals were first synthesized and incorporated into Matrimid matrix.•DFT calculation implied the amine group on DETA was bonded to Mg2+ sites via Mgδ+···Nδ- interaction.•Mg2(dobdc) and DETA-bridged Mg2(dobdc) crystals attain CO2 uptake of 7.15 and 6.45 mmol/g.•DETA molecules play an important role in filling interface defect in MMMs, acting as intermediate agent.•15-DETA-Mg-M exhibits optimal CO2 permeability of 41.1 Barrers, 3.03 times higher than Matrimid.