Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 117585, Singapore.
Institute of Sustainability for Chemicals, Energy and Environment, Agency for Science, Technology and Research, Jurong Island, Singapore 627833, Singapore.
Proc Natl Acad Sci U S A. 2023 Feb 28;120(9):e2217081120. doi: 10.1073/pnas.2217081120. Epub 2023 Feb 22.
Carbon capture is one of the essential low-carbon technologies required to achieve societal climate goals at the lowest cost. Covalent organic frameworks (COFs) are promising adsorbents for CO capture because of their well-defined porosity, large surface area, and high stability. Current COF-based CO capture is mainly based on a physisorption mechanism, exhibiting smooth and reversible sorption isotherms. In the present study, we report unusual CO sorption isotherms featuring one or more tunable hysteresis steps with metal ion (Fe, Cr, or In)-doped Schiff-base two-dimensional (2D) COFs (Py-1P, Py-TT, and Py-Py) as adsorbents. Synchrotron X-ray diffraction, spectroscopic and computational studies indicate that the sharp adsorption steps in the isotherm originate from the insertion of CO between the metal ion and the N atom of the imine bond on the inner pore surface of the COFs as the CO pressure reaches threshold values. As a result, the CO adsorption capacity of the ion-doped Py-1P COF is increased by 89.5% compared with that of the undoped Py-1P COF. This CO sorption mechanism provides an efficient and straightforward approach to enhancing the CO capture capacity of COF-based adsorbents, yielding insights into developing chemistry for CO capture and conversion.
碳捕集是实现社会气候目标所需的最低成本的低碳技术之一。共价有机框架（COFs）因其具有明确的孔隙率、大的表面积和高的稳定性而成为有前途的 CO 捕获吸附剂。目前基于 COF 的 CO 捕获主要基于物理吸附机制，表现出平滑和可逆的吸附等温线。在本研究中，我们报告了异常的 CO 吸附等温线，其特征是具有一个或多个可调谐滞后步骤，金属离子（Fe、Cr 或 In）掺杂席夫碱二维（2D）COFs（Py-1P、Py-TT 和 Py-Py）作为吸附剂。同步加速器 X 射线衍射、光谱和计算研究表明，等温线中的尖锐吸附步骤源于 CO 在 COF 内孔表面的金属离子和亚胺键的 N 原子之间的插入，当 CO 压力达到阈值时。结果，与未掺杂的 Py-1P COF 相比，掺杂离子的 Py-1P COF 的 CO 吸附容量增加了 89.5%。这种 CO 吸附机制为增强基于 COF 的吸附剂的 CO 捕获能力提供了一种有效且直接的方法，为 CO 捕获和转化的化学发展提供了新的思路。
