Research Of Adsorbing Low Concentration CO₂ With MOF-74 Series Of Metal-Organic Frameworks

It is now widely accepted that CO2 emitted from human activities is causing global war-ming via the greenhouse effect. Recovery of CO2 is significantly important to mitigate the green effect and to use of resources optimally. Therefore, there is an urgent need to develop efficient CO2 adsorbents. Metal-organic framework is a new porous material and has attracted both academic and industrial attentions for their potential applications in gas separation and storage. MOF-74 series exhibit a honeycomb-type network topology featuring hexagonal one-dimensional channels with a high density of exposed metal ion adsorption sites. Therefore, MOF-74 materials'adsorption performance is excellent.The effect of velocity of feed gas and adsorbent temperature on CO2 adsorption performance were investigated by using Mg-MOF-74. The result showed that the breakthrough time and adsorption capacity decrease with the rising of velocity and adsorbent temperature. The adsorption capacity of Mg-MOF-74 reduced with the rising of temperature, illustrating that its adsorption to CO2 belonged to physical adsorption, and low temperature was beneficial to the adsorption to CO2. Using solvothermal method to synthesize materials of the M-MOF-74 series (M=Cu, Zn, Co, Mn, Mg, Cd, et al), and exploring the differences of adsorption capacity to CO2 for MOF-74 materials synthesized by different metal ions. Between this series of materials, the Cu-MOF-74's adsorption capacity was the worst. The Mg-MOF-74's was the best, and the adsorption performance was much better than other materials.Synthesizing Mg-MOF-74 materials with solvothermal method, having impregnate and load on Mg-MOF-74 with aqua ammonia of various concentrations, exploring influence law of impregnated ammonia with various concentrations on modified materials'adsorption performance of CO2. The result shows that the process of ammonia loading can decrease the effect of CO2 concentration on material's adsorption performance effectively, though the process of ammonia loading reduces materials'specific surface area, it increases material's adsorption capacities on per unit surface area, the process of ammonia loading is good for materials'adsorption on low-concentration CO2. Among modified materials, the adsorption performance of materials which impregnated and loaded with 0.2mol/L aqua ammonia was superior to raw materials and its adsorption capacity was 200.5mg/g, the adsorption capacity has been increased by 5.6% as compared with raw materials without impregnated.Two MOF-74 analogs with OH groups on 1D channel surfaces have been synthesized through multi-component self-assembly at room temperature and atmospheric pressure. These analogs are named Zn(OCA-OH)2(4,4'-bipy)o.s and Zn(MCA-OH)2(4,4'-bipy)o.s, respectively. Analog's structure and pore size is consistent with MOF-74. We explored the differences of CO2 adsorption performance between two analogs and Zn-MOF-74. The result showed that the adsorption performance of Zn(OCA-OH)2(4,4'-bipy)0.5 and Zn(MCA-OH)2(4,4'-bipy)0.5 on CO2 especially CO2 with low-concentration is superior to Zn-MOF-74. Besides, the adsor-ption performance of Zn(MCA-OH)2(4,4'-bipy)0.5 on 3%CO2 is superior to Zn(OCA-OH)2(4, 4'-bipy)0.5 slightly.