Preparation And Evaluation Of Hybrid MOFs For CO₂ Adsorption

Carbon capture, utilization and storage（CCUS） is considered to be one of the effective methods to alleviate greenhouse effect. Recently, adsorption using solid adsorbents has been proved to be an efficient method for post-combustion CO₂ capture in terms of its fast adsorption rate, mild operating conditions and lower energy penalty. In this regard, a wide range of CO₂ adsorbents were developed such as silicon-based materials, carbon-based materials, zeolites and so on. Among these, metal-organic frameworks（MOFs） occurred to be a promising option owing to their ultrahigh porosity and versatile framework functionalities.Combining MOFs with other materials has been proposed recently to integrate merits and mitigate shortcomings of both the components. To date, MOF composites have been successfully fabiricated with components including metal nanoparticles, metal oxides, polymers, graphene, carbon nanotubes, silicon-based materials and so forth. In this dissertation, siliceous mesocellular foam（MCF） was used for the synthesis of MOF composites, and the surface of MCF was modified with different functionalities in order to investigate their effect on the formation of MOF composites and the CO₂ adsorption performance of resulted composites.A series of compositing materials comprise HKUST-1 and MCF was firstly fabricated following a one-pot method, the effect of MCF functionalization on the formation, structure properties, and performance in CO₂ adsorption of the composting materials was investigated. All the composites were interestingly showing higher CO₂ uptakes as compared with either the pure HKUST-1 or the MCF-x owing to the change of microporous pore size distribution and newly introduced mesoporous structures. The best performing sample, HK#MCF-NH2, exhibited a promising CO₂ adsorption capacity of 3.89 mmol/g（25 oC, 1 bar） with excellent cyclic stability（25 cycles） and selectivity over N2.Based on the above results, the preparation conditions of HK#MCF-OH composites was optimized, these including the MCF-OH content in the precursor solution, synthesis temperature and duration. The results show that the best synthesis condition in terms for maximing CO₂ adsorption capacity includes: MCF-OH content is 5 wt%, using DMF as the synthetic solvent at 75 oC and 24 h. Then the influence of the types of the grafted amines for the MCF-NH2 and its content in the precursor solution were investigated. The results indicated that the sample HK#MCF-1N showed the best CO₂ adsorption performance, and composites would have the optimal performance of CO₂ adsorption when the content of MCF-1N in the precursor is 5 wt%.Based on the above findings, composites of MIL-101, UiO-66 with hydroxyl group functionalized siliceous mesocellular foam（MCF-OH） were prepared by in-situ solvothermal method. The effect of MCF-OH on the structure properties, and performance in CO₂ adsorption of the composting materials was investigated. It was found that the influence on the morphology of MOFs varied due to the different central metals in MOFs. For the two composites, the growth of MOFs crystal particles was restricted, leading to the formation of smaller MOFs crystal particles and higher BET surface areas than the pure MOFs, which is different as compared with HK#MCF-OH composites. All the two composites showed higher CO₂ adsorption capacities than the pure MOFs, but the increment are lower than HK#MOF-OH composite.