Experimental Studies On The Synthesis And Gas Adsorption Properties Of Hf-Based Stable Metal-Organic Frameworks

Metal-organic frameworks (MOFs) are a new class of nanoporous materials with high surface area, large porosity, tunable pore size and structure diversity. Interest in MOFs has sharply increased due to their wide applications such as gas storage, separation, catalysis, and drug delivery. However, most of MOFs cannot remain stable in industrial operation conditions such as in water environment, thus limit their applications. Therefore, in view of the problems such as the instability of the materials, we synthesize a series of stable Hf-MOF materials through solvothermal method, and their applications to gas separation were studied. The main contents are as follows:1. High quality UiO-66(Hf) material was synthesized by a high temperature and high concentration method. The experiment results show that this MOF has excellent chemical and thermal stability. In order to further improve the performance of this material for gas separation, a series of UiO-66(Hf) based MOFs were synthesized by using three types of organic ligands with different functional groups. The synthesized MOF materials were characterized by XRD, TGA, N2adsorption and SEM measurements.2. In order to expand the pore size, the ligand-extension strategy was employed in the design and synthesis of Hf-MOFs. In this work, by using various types of linkers with different length, three Hf-MOF materials with different pore sizes were designed and synthesized. The chemical and thermal stabilities of the MOFs were systematically investigated; we found that Hf-FUM and UiO-66(Hf) are water-resistant except Hf-BPDC. It means that the chemical stability of the material is reduced with the increase of the length of the ligand.3. In order to further understand the gas separation performance of Hf-MOF material with different pore sizes, we measured the adsorption isotherms of CO2, CH4and N2at298K. The results show that Hf-FUM with the smallest pore size has the best separation performance. The conclusion obtained in this work may provide theoretical guidance for the design and synthesis of new nanoporous materials towards the applications in industry separation system.