Enhancing CO2 capture capacity and selectivity in UTSA-16(Co) via elevated-temperature synthesis for flue gas separation

초록

A major challenge in designing metal-organic frameworks (MOFs) for post-combustion CO2 capture is to enhance adsorption capacity without altering the underlying topology or decreasing selectivity. Herein, we report a straightforward elevated-temperature synthesis strategy to optimize the adsorption performance of the KCo3 (UTSA-16(Co)) MOF. The synthesis of MOF at elevated temperatures (120-160, 190, and 210 degrees C) yielded the optimal material UTSA-16@190, which undergoes a subtle local lattice relaxation, leading to a distinct expansion that significantly enhances its structural porosity. Compared with pristine UTSA-16@120, the thermally modulated material showed a 40% increase in surface area, a 34% increase in pore volume, an 8.6% increase in accessible volume, a 4.1% increase in accessible surface area, and a 78% reduction in particle size. This structural dilation optimizes internal pore connectivity by eliminating isolated micro-voids, thereby establishing continuous conduction pathways. These factors collectively enhance both CO2 adsorption capacity and selectivity. Under simulated flue-gas conditions at 308 K, UTSA-16@190 demonstrated a 79% enhancement in CO2 uptake (1.96-3.51 mmol/g) and a 33% enhancement in CO2/N2 selectivity (236-315), while maintaining full capacity over 50 consecutive adsorption-desorption cycles. Moreover, the thermally modulated framework exhibited robust performance in the presence of flue gas impurities (SOx, NOx, O2, and humidity), with a maximum 27% loss in adsorption performance under humid conditions. Overall, this work highlights the potential of elevated-temperature synthesis as a practical approach to producing high-performance materials, paving the way for their practical applications in industrial settings.

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