I-Corps: Materials for CO2 Capture

二氧化碳作为污染物或杂质出现在石油工业的混合气体中，由于二氧化碳排放对环境的影响，立法者开始要求将二氧化碳从燃烧产物中分离出来。因此，二氧化碳分离是发电厂、重工业、氢气生产、天然气脱臭和空气净化厂等行业的一个问题。然而，目前可用的二氧化碳分离选择有限且不经济。一种当代的方法是吸收，这是一种成熟的、但能源密集型和昂贵的方法。例如，基于广泛使用的吸收剂单乙醇胺(MEA)的化学吸收基准，由于溶剂再生的高昂成本，目前每公吨二氧化碳的成本超过70美元；总体而言，使用传统技术捕获发电厂的二氧化碳排放需要工厂能源输出的20%-30%。这一高昂的成本是二氧化碳捕获技术在工业上广泛采用的最大障碍。因此，工业迫切需要开发高性能和低成本的技术和材料，以实现资本效率高的二氧化碳捕获。一种有前景的二氧化碳捕获替代方法是多孔材料吸附：用于二氧化碳分离的候选吸附剂应该选择性地从气体混合物中吸附二氧化碳，并具有较大的表面积以将二氧化碳分子容纳到孔隙中。基于I-Corps团队成员最近开发的一种新型、合适的吸附剂，该项目的目标是将一系列新的吸附剂(沸石咪唑骨架或ZIF)商业化，这些吸附剂表现出从其他气体中分离二氧化碳的卓越选择性，并且具有巨大的表面积来存储二氧化碳。这项技术是在二氧化碳捕集市场的关键时刻开发的。美国政府以及加拿大、中国和欧盟等其他几个国家和实体都实施了严格的排放标准，但目前还没有最优甚至现有的产品来满足所需的需求。建议的ZIF具有出色的高选择性二氧化碳捕获能力，因此在市场需求旺盛的时候提供了一个革命性的解决方案。金属有机骨架(MOF)是由有机连接体和含金属结点构成的杂化多孔材料。MOF提供的典型比表面积--因此，气体吸附能力--比沸石高一个数量级。ZIF是MOF的一个子家族。它们具有M(Im)4沸石型骨架，其中四面体元素M是通过咪唑(Im)部分桥联的过渡金属。ZIF可以吸附二氧化碳排放，在需要再生之前存储的容量是现有吸附剂的五倍。例如，每个单位体积的ZIF-69可以储存高达其体积的83倍的二氧化碳。此外，ZIF可以表现出高的化学和热稳定性，因此可以作为稳健的二氧化碳捕获过程。在这项全面的研究中，我们建议合成一种新的ZIF亚类，通过基于蒙特卡罗的模拟表明，与等结构ZIF相比，ZIF具有100倍的二氧化碳捕获能力。CO2捕集能力的增加伴随着对CH4、H2和N2的捕获能力的微乎其微的变化；因此，CO2对其他气体的吸收比显著增加，表明我们的新型ZIF对CO2分离具有非常高的选择性。这套能力可以显著降低燃烧发电厂、重工业、天然气加工和氢气生产公司的碳分离和捕获成本。

CO2 appears as a contaminant or impurity in gas mixtures in oil industries, and because of the environmental impacts of CO2 emissions, lawmakers are beginning to require the separation of CO2 from combustion products. Consequently, CO2 separation is an issue in power plants, heavy industries, hydrogen production, natural gas sweetening, and air purification plants, among other industries. However, the currently available options for CO2 separation are limited and uneconomical. One contemporary method is absorption, a well-matured but energy-intensive and expensive approach. For example, the benchmark for chemical absorption based on monoethanolamine (MEA), a widely used absorbent, currently imposes costs of over $70 per metric ton of CO2 due to the high cost of solvent regeneration; overall, capturing CO2 emissions from power plants using conventional technologies requires 20-30% of the plant's energy output. This high cost is the single largest obstacle for the widespread industrial adoption of CO2 capture technologies. Therefore, industry has an urgent need for the development of high-performance and low-cost technologies and materials that enable capital-efficient CO2 capture. A promising alternative process for CO2 capture is adsorption by porous materials: candidate adsorbents for CO2 separation should selectively adsorb CO2 from gas mixtures and have large surface areas to accommodate CO2 molecules into the pores. Based on a novel, suitable adsorbent recently developed by members of the proposed I-Corps team, the aim of this project is to commercialize a new series of adsorbents (zeolitic imidazolate frameworks, or ZIFs) that exhibit superior selectivity for separating CO2 from other gases and that have significant surface area to store it. This technology has been developed at a critical time for the CO2 capture market. Strict emission standards have been imposed by the U.S. government and several other countries and entities such as Canada, China, and the European Union, but there is not yet an optimal or even existing product available to meet the required needs. The proposed ZIF, with its outstanding capability for high-selectivity CO2 capture, therefore provides a revolutionary solution at a time of severe market need. Metal-organic frameworks (MOFs) are hybrid porous materials constructed from organic linkers and metal-containing nodes. The typical specific surface areas - and hence, gas adsorption capacities - that MOFs provide are an order of magnitude higher than those of zeolites. ZIFs are a subfamily of MOFs. They have an M(Im)4 zeolite-type framework in which tetrahedral elements, M, are transition metals bridged by imidazolate (Im) moieties. ZIFs can adsorb CO2 emissions and store five times more than existing adsorbents before requiring regeneration. For example, each unit volume of ZIF-69 can store up to 83 times its volume in CO2. Moreover, ZIFs can exhibit high chemical and thermal stability, and therefore can be robust processes for CO2 capture. In this comprehensive study, we propose the synthesis of a new subclass of ZIFs that, as indicated by Monte-Carlo-based simulation, have a 100-fold-increased CO2 capture capacity compared to the isostructural ZIFs. This increase in CO2 capture capacity was accompanied by only negligible changes in capture capacity for CH4, H2, and N2; therefore, the uptake ratio of CO2 to the other gases increased significantly, indicating very high selectivity for CO2 separation in our novel ZIFs. This set of abilities could significantly reduce the cost of carbon separation and capture at combustion-based power plants, heavy industries, natural gas processing, and hydrogen production companies.