Water-stable composite of HKUST-1 with its pyrolysis products for enhanced CO2 capture capacity

Parent metal–organic framework (MOF), especially HKUST-1, is difficult to achieve both high CO2 adsorption capacity and excellent water stability. We proposed an innovative strategy to prepare novel composites of HKUST-1/x (x, pyrolysis temperature = 400, 600, 800 ℃) by the combination of parent HKUST-1 and its pyrolysis products. SEM, FT-IR and XRD characterization results verified the successful modification of the samples. The adsorption isotherm curves of N2 and CO2 showed that HKUST-1/800 had the highest specific surface area (1817 m2·g−1), pore volume (0.802 cm3·g−1) and CO2 adsorption capacity (9.02 mmol·g−1, at 273 K and 1 bar), which exhibited a significant enhancement effect. As well as, the CO2/N2 (15:85) selectivity of HKUST-1/800 was 2.4 times higher than that of pure HKUST-1. In addition, the hydrophobicity and water stability of HKUST-1/800 were improved significantly. The water contact angle (WCA) of HKUST-1/800 reached 82.5°, 3.5 times higher than that of pure HKUST-1, and HKUST-1/800 retained most of the CO2 adsorption capacity (5.46 and 4.31 mmol·g−1) after soaking in water for 1 and 5 days, respectively. However, HKUST-1 lost the majority of its adsorption capacity (retained only 0.91 and 0.74 mmol·g−1). The increase in the number of Cu sites and the formation of hydrophobic microenvironment on the surface were the reasons for its excellent adsorption capacity and water stability. Above of all, these hold a great potential for carbon capture applications in humid environments.