Synthesis Of Metal-Organic Frameworks And Their Applications In Gas-/Liquid-phase Separation

In recent years, metal-organic frameworks (MOFs) have attracted extensive attention in gas sorption, separation and catalysis due to their uniform pore size, crystallinity, structural diversity, high tunability and very high surface area. Despite this, most of MOFs are actually sensitive toward moisture/water and it is challenging for practical application. In this dissertation, we have designed and synthesized two novel and stable MOFs and investigated their applications in CO2sorption and conversion as well as oil recovery from water.1. Synthesis of two stableMOFsA stable A1-based MOF, denoted as USTC-253(USTC=University of Science and Technology of China), has been synthesized based on the reaction of A1(NO3)3·9H2O and4,4’-dibenzoic acid-2,2’-sulfone (Sbpdc) at120℃. It was characterized by H-NMR, XRD, infrared spectroscopy, etc. Stability studies have indicated that the framework of USTC-253-TFA remains very well after being stored in humid environment for over28h.The other novel and highly stable MOF involving corrugated-CF3surface that features high hydrophobicity has been synthesized based on the reaction of CuCl2·2H2O and4,4’-(hexafluoroisopropylidene)diphthalate at85℃. It was characterized by single crystal X-ray diffraction and XRD and denoted as USTC-6. Stability studies have indicated that USTC-6retains its framework in water for over2month and it is even stable in solutions with pH ranging from2to10up to7days.2. Application of USTC-253for CO2sorption and conversion. A sulfone-functionalized metal-organic framework (MOF), USTC-253, has been synthesized and it exhibits much higher (168-182%) CO2uptake capacity than the corresponding unfurnished MOFs (273K, latm). The introduction of trifluoroacetic acid (TFA) during the synthesis of USTC-253affords defects-involved USTC-253-TFA with exposed metal centers, which allows further increasing CO2uptake by167%compared to that of pristine USTC-253. The USTC-253-TFA exhibits a very high IAST selectivity (S=75) to CO2over N2at298K. In addition, USTC-253-TFA demonstrates great catalytic activity and recyclability in cycloaddition of CO2and epoxide at room temperature under1atm CO2pressure, due to the presence of Lewis acid and BrΦnsted acid sites, which have been well evaluated by DRIFT spectroscopy with a CO probe molecule. Simutaneously, it is proposed that the CO2adsorption capability is in a positive correlation with the catalytic performance toward the CO2conversion.3. Application of USTC-6for pumping recovery of oil spill from waterThe water contact angle of USTC-6was determined to be121°and it has been demonstrated to be very stable in water. The uniform growth of USTC-6throughout the graphene oxide (GO)-modified sponge has been achieved to yield a macroscopic MOF@GO@sponge sorbent, which repels water and exhibits superior adsorption capacity for diverse oils and organic solvents. This hierarchically porous sorbent takes up as high as1200-4300wt%of organic pollutants and oils and it can separate oil/organic solvents from water by adsorption and sequeezing. Remarkably, the sorbent has been further assembled with tubes and a self-priming pump to build a model apparatus that is able to afford consecutive and efficient oil recovery from water. The easy and fast recovery of oils/organic solvents from water based on such apparatus make it great potential for future water purification and treatment.