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

Abstract

The composite adsorbent of HKUST-1 with its pyrolysis products has excellent water stability and CO 2 capture capacity. • Synthesis of HKUST-1 and its pyrolysis products to prepare a novel CO 2 adsorbent. • The BET and V total of HKUST-1/x increased significantly compared with pure HKUST-1. • HKUST-1/800 had the highest CO 2 capacity of 9.02 mmol·g -1 at 273 K and 1 bar. • The CO 2 /N 2 (15:85) selectivity of HKUST-1/800 was 106. • HKUST-1/800 still maintained excellent CO 2 adsorption amounts after soaking in water. Parent metal-organic framework (MOF), especially HKUST-1, is difficult to achieve both high CO 2 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 N 2 and CO 2 showed that HKUST-1/800 had the highest specific surface area (1817 m 2 ·g -1 ), pore volume (0.802 cm 3 ·g -1 ) and CO 2 adsorption capacity (9.02 mmol·g -1 , at 273 K and 1 bar), which exhibited a significant enhancement effect. As well as, the CO 2 /N 2 (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 CO 2 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.