An investigation of a series of layered Zn-1,4-diazabicyclo[2.2.2]octane metal–organic frameworks: local structure and adsorption properties of mixed-metal centre

The mixed-metal pillar-layered metal–organic frameworks of Zn(bdc)(DABCO) 0.5 , Zn 0.5 Cu 0.5 (bdc)(DABCO) 0.5 and Cu(bdc)(DABCO) 0.5 (bdc = 1,4-benzenedicarboxylate, DABCO = 1,4-diazabicyclo[2.2.2]octane) are investigated for their local structures and gas adsorption properties. According to the obtained electron paramagnetic resonance (EPR) spectra, the distorted structures around Cu 2+ are proposed to be tetragonally and orthorhombically elongated [CuO 4 N] with the well fitted high-order perturbation formulae of the EPR parameters. Due to the doped Cu 2+ , the adsorption isotherms of industrially relevant gases (CO 2 , CO, CH 4 and N 2 ) and lower alkanes (CH 4 , C 2 H 6 , C 3 H 8 , C 4 H 10 and C 5 H 12 ) are different, especially at different temperatures. By combining the structural properties and adsorption isotherms, a comprehensive study suggests that the ZnDABCO series can be a controllable tool in gas storage and separation.