Adsorption of carbon dioxide on Cu_xMg_y(BTC)₂ MOFs: influence of Cu/Mg ratio

A series of bimetallic metal-organic frameworks (Cu_xMg_y(BTC)₂ MOFs) was synthesized. The as-produced MOFs were described utilizing different characterizations techniques. The dynamic adsorption efficiencies of the prepared MOFs toward the carbon dioxide (CO₂) from the nitrogen stream at separate temperatures and various total levels of flow were achieved including the evaluation of the suitable kinetic model. The results showed that copper ions could be substituted successfully by magnesium ions up to molar ratio 1:1 (Cu_1.5Mg_1.5(BTC)₂ MOF), without obvious deformation in the crystalline structure of the parent Cu₃(BTC)₂.3H₂O (HKUST-1). In all of the as-synthesized MOFs, the introduction of magnesium ions to the context of Cu-BTC had accompanied changes in the morphological structure, porosity, and thermal behavior. The Cu_1.5Mg_1.5(BTC)₂ MOF showed significant enhancing on its CO₂ adsorption capacity (23.85 mmol/g) compared with Cu-BTC MOF (5.95 mmol/g) and Mg-BTC MOF (4.57 mmol/g), which indicated the key-role of the central metals in the MOF in CO₂ adsorption. The second-order kinetic studies suited the experimental work with more precise than pseudo-first-order. Also, the reusability of the bimetallic adsorbent under the optimum temperature and flow rate was evaluated for 5 cycles.