With the help of the Advanced Light Source (ALS), researchers from UC Berkeley and ExxonMobil fine-tuned a material to capture CO2 in the presence of water.
About 65% of anthropogenic greenhouse gas emissions comes from the combustion of fossil fuels in power plants. So far, efforts to capture CO2 from power-plant flue gases and sequester it underground have mainly focused on coal-fired power plants. However, in the United States, natural gas has surpassed coal in the amount CO2 released, despite the fact that natural gas emits approximately half as much CO2 per unit of electricity. Therefore, new materials are urgently needed to address this situation.
Not all combustion is alike
Compared to coal-fired power plants, natural gas combined cycle (NGCC) plants produce flue gases with low CO2 concentrations. This reduces the carbon footprint, but increases the technical difficulty of CO2 capture. Also, materials capable of adsorbing such low concentrations of CO2 often require high temperatures to release it for sequestration, an important part of the cycle that offsets initial low-carbon benefits. NGCC emissions also have a higher concentration of O2, which has a corrosive effect on adsorbent materials, and both NGCC and coal flue streams are saturated in water, which can both degrade materials and reduce efficiency. Thus, an effective NGCC CO2-capture material must selectively bind low-concentration CO2 under humid conditions while being thermally and oxidatively stable.
Image: Single-crystal x-ray diffraction enables the precise determination of the positions of the atoms in metal–organic frameworks (MOFs), highly porous materials capable of soaking up vast quantities of a specific gas molecule, such as CO2. This structure represents 2-ampd–Zn2(dobpdc), a MOF with the same structure as 2-ampd–Mg2(dobpdc), the subject of this study. Light blue, blue, red, gray, and white spheres represent Zn, N, O, C, and H atoms, respectively.