Construction of a dual-cage-based MOF with uncoordinated nitrogen sites for CO2 adsorption and fixation

A new dual-cage-based porous metal-organic framework (MOF, termed DZU-113) assembly from the triazole-carboxylate linker and the Cu(II) paddle-wheel unit was solvothermally constructed. The structure of DZU-113 was determined by single-crystal X-ray diffraction, being consisted of the octahedral cage with an internal diameter of approximately 0.4 ​nm, and the spindle nano-cage with internal pores of about 0.8 ​nm ​× ​2.2 ​nm, respectively. Specially, the uncoordinated N atoms of triazole groups are distributed in the bottleneck windows of the spindle nano-cage, serving as open functional sites. DZU-113 has permanent porosity with the Brunauer−Emmett−Teller surface area of 1207 ​m2 ​g−1. The CO2 adsorption test demonstrated that the total uptake of DZU-113 can reach 66.7 ​cm3 ​g−1 ​at 298 ​K, and 112.0 ​cm3 ​g−1 ​at 273 ​K, 1 ​bar. Moreover, it achieves robust catalytic performance for the cycloaddition of CO2 and epoxides under mild conditions.