Metal-organic frameworks: Their microwave synthesis and applications as adsorbents for preconcentration.

摘要

My thesis contains three major parts. In the first part of this work, a detailed investigation has been carried out to explore the potential of using MOFs as adsorbent for trapping and preconcentration on a portable micro gas detector. A well-known IRMOF1 was tested as preconcentration adsorbent for the first time using dimethly methylphosphonate (DMMP) as a test case. DMMP is a simulant of nerve agent. We find that DMMP is selectively adsorbed on IRMOF1 and is easily released upon heating to 250°C. Concentration gains of more than 5000 were observed for DMMP with a 4-s sampling time. Sorption capacities are 0.95 g of DMMP/g of IRMOF1. By comparison, dodecane shows a preconcentration gain of ∼5 under similar conditions. These results demonstrate that MOFs can be quite useful in selective preconcentrators.; In the second part, we have developed a new method for rapid synthesis of MOFs, which we named "microwave-assisted solvothermal synthesis" (MASS). So far most of the reported MOF syntheses were either solvothermal or hydrothermal syntheses, which took from half a day to few weeks. Here we show that MASS method allows many reported MOF crystals to be synthesized in under a minute. The properties of the crystals made by MASS method are of the same quality as those produced by the standard solvothermal method, but the synthesis is much more rapid and resulting MOF crystal are no longer dependent on the initial nucleus and wall conditions. The homogeneous effects of microwave could create a uniform seeding condition, therefore the size and shape of the crystals can be well controlled by simply changing a few reaction conditions.; MASS method provides us a simple and fast approach to quickly build a library of other new MOFs. In the third part, we demonstrate the syntheses of 14 new MOF materials based on the MASS method. Each has been tested by TGA to explore its sorption behavior with 4 different vapors. The structures for 3 of our new MOFs are solved based on the single X-ray analysis, and their sorption features are investigated based on the structure information.