| In recent years, a new family of hybrid nanoporous materials, metal-organic frameworks (MOFs), has attracted considerable interest, because of their large specific surface areas, pore volumes and potential applications in gas sorption, separation, catalysis and chemical sensing devices. There are thousands of MOFs reported by now, and the MOFs to be synthesized is unlimited in principle. Due to the structures of MOFs are diverse and complex, pure experimental approach is not enough to promote efficiently development and application of MOFs. In this respect, it is necessary to introduce computational chemistry to the study of MOFs.For apractical application, MOFs should have high thermal stability to keep permanent porosity after removal of solvent molecules. However, this is difficult for most MOFs with large pores which are much easier to collapse or shrink into nonporous frameworks after guest removal. In this work, we study a series of stable MOFs using experimental measurements in combination with molecular simulations. The main works are:1. The cooperative effect of temperature and linker functionality on CO2capture in MOFs was investigated using experimental measurements in combination with molecular simulations. To do this, four MOFs with identical topology but different functional groups on the linkers and three important CO2-containing industrial gas mixtures were adopted. The interplay between linker functionality and temperature was analyzed in terms of CO2storage capacity, adsorption selectivity, working capacity of CO2in temperature swing adsorption (TSA) processes, as well as sorbent selection parameter (Sssp). The results show that when we design a new MOF for a certain CO2capture process operated at a certain temperature, the MOF should be designed to have maximized affinity for CO2but with a negligible or small effect caused by the reduction of free volume at that temperature and the corresponding operating pressure.2. A new porous Zr-based MOF was synthesized by the solvothermal method using2,6-naphthalenedicarb-oxylic acid (NDC) as the organic linker, and its luminescent performance and stability were investigated systematically. The material synthesized exhibits quite high chemical stability in addition to exceptional high thermal stability, better than the existing luminescent MOFs. The experiments combining with com-putations indicate that the electron transfer from inorganic moieties to organic moieties contributes to the luminescent behavior of the Zr-NDC MOF besides the NDC ligand. As far as we know, this is the first study of investigating the luminescent behaviors of such Zr-based MOFs. Moreover, the cycling measure-ments demonstrate an interesting prospect for the long-term reusability of this material. The results obtained in this work may provide useful information for the design of physicochemically stable MOFs with permanent porosity in sensing applications in the future.3. Enhanced CO2adsorption and separation capability in Zr-based MOFs was achieved by introducing-NO2,-NH2or-SO3H groups into pore surface of a platform MOF, Zr-NDC. Molecular simulation was firstly used to predict the properties of these materials, which showed that CO2adsorption and separation capability can be improved through importing these functional groups. Two analogues, Zr-NDC-2NO2and Zr-NDC-2SO3H were then synthesized by using new ligands, NDC-2NO2and NDC-2SO3H, and checked for their applications. Compared to Zr-NDC, Zr-NDC-2NO2and Zr-NDC-2SO3H showed an obviously enhanced CO2adsorption capacities and separation selectivity over N2, notwithstanding pores reduced because of adding these functional groups. Particularly, introducing-2SO3H groups has led to a double gravimetric and triple volumetric increase of CO2adsorption and a very high CO2/N2separation selectivity.4. A series of UiO-66/GO composite materials (UiO-66-5%-GO, UiO-66-10%-GO and UiO-66-15%-GO) have been prepared through in-situ synthesied method. The introduction of GO reduce the surface area of composites in different degree. However, introducing GO has led to increase of CO2adsorption and high CO2/CH4, CO2/N2and CO2/CO separation selectivity.5. ZnobbTED, ZncbbTED and ZnhfbbTED were synthesized by using solvent thermal synthesis method. This series of MOFs use the classical dizinc-paddle-wheel carboxylate SBU, and triethylene-diamine was used as the secondary ligand. The CO2storage capacity and adsorption selectivity of this series of MOFs were studied using molecular simulation method. Particularly, ZnobbTED can serve as the CO2capture material candidates in low pressure application. |
