Effect of various alkaline agents on the size and morphology of nano-sized HKUST-1 for CO2 adsorption

Abstract

Two type of modulators, including sodium acetate and triethylamine were used to synthesize nanosized HKUST-1 crystals with tailored size and morphology using a coordination modulation method. The results of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N₂ sorption isotherms confirm that the size of the HKUST-1 crystals can be tuned from the micron scale to the nanoscale through precise modulation of the amounts of the modulators. Moreover, hierarchical porous structures are obtained with the addition of modulators. It is suggested that a moderate acid–base environment and capping groups play an important role in controlling the size and morphology of HKUST-1. Dynamic CO₂ breakthrough experiments illustrate that the CO₂ capacity of nanosized HKUST-1 crystals is superior to that of micron-sized HKUST-1 crystals under low CO₂ partial pressure conditions (0.1 bar). Besides, the CO₂ adsorption capacity of nanosized HKUST-1 crystals was maintained after ten adsorption/desorption cycles.