Construction of Zn-Cu bimetallic metal-organic frameworks for carbon dioxide capture

Bimetallic metal-organic frameworks (MOFs) have shown more impressive performance in gas adsorption compared with monometallic MOFs. Herein, a Cu-Zn bimetallic metal-organic framework (Zn/Cu-BTC) was synthesized via a one-pot method, and its structure, thermal stability and CO₂ adsorption property were investigated and compared with those of corresponding monometallic Cu-BTC and Zn-BTC. The results showed that Zn/Cu-BTC has a specific ortho-octahedral crystal morphology with a unique X-ray diffraction peak, the atomic ratio of Zn to Cu is about 1 : 5, and it remained stable at a temperature up to 490 K. In Zn/Cu-BTC, Cu²⁺ played a role in increasing the specific surface area and porosity of the MOF and improving the gas adsorption performance. The CO₂ adsorption of Zn/Cu-BTC is lower than that of Cu-BTC but much higher than that of Zn-BTC, and CO₂ adsorption heat was 30.52 kJ mol^-1, which indicated physical adsorption. In addition, Zn/Cu-BTC had higher CO₂/N₂ adsorption selectivity compared with Zn-BTC and Cu-BTC, with a maximum value of 17. This study can be a reference for the research on improving the adsorption selectivity of gases by constructing bimetallic MOFs.