Ultrafast room temperature synthesis of novel composites Imi@Cu-BTC with improved stability against moisture

Abstract

Most of MOFs are unstable under moist circumstances, which hinders their practical applications. And thus, we propose a new strategy to enhance the steam stability of Cu-BTC (HKUST-1). In this work, Cu-BTC was functionalized with imidazole (Imi) to yield Imi@Cu-BTC. The novel Imi@Cu-BTC can be quickly synthesized within 1-min at room temperature. Successful incorporation of Imi on Cu-BTC was proved by FT-IR spectra. The as-synthesized Imi1/3@Cu-BTC was of a decent BET surface area up to 1694m2/g, and exhibited a high CO2 adsorption capacity of 4.4mmol/g at 1bar and room temperature, which was well above that of ZIF-8, UiO-66 and MIL-101. More interestingly, the steam stability of Imi@Cu-BTC was significantly improved compared to that of Cu-BTC. While Cu-BTC almost lost all its crystallinity and only retained 6% of its original CO2 capacity after being exposed to humid air for 20days, Imi1/3@Cu-BTC managed to preserve its main crystal structure and preserved 78% of its initial CO2 capacity after the exposure. The origination of the improved steam stability of Imi@Cu-BTC was interpreted by DFT calculations. In conclusion, the strategy of incorporating Imi into Cu-BTC is very efficient in improving its structure stability against moisture due to the protection of Cu sites from Imi, and the ultrafast room temperature synthesis is promising for the scalable production of MOF-based materials.