In Situ Investigation of CO2 Sorption on Mixed-Metal Citrates

The objective of this experiment is to determine the distribution and local coordination of transition metals in MOF materials designed for CO2 capture. A series of alkali metal–transition metal citrate dihydrates with the general sample formula (MI)2(MII)3(C6H4O7)2·2H2O, where MI=Li,Na,K; MII=Fe,Co,Ni,Zn will be investigated. Starting composition is K2Co3(C6H4O7)2·2H2O, other metals will partially substitute the principal ones.

The experiment will be conducted ex situ as well as in situ under CO2 absorption at ambient conditions using a multipurpose gas reactor. XANES and EXAFS data will be collected at Fe, Co, Ni, and Zn K-edges. Depending on available time, additional in situ experiments under controlled humidity will be conducted to assess the influence of water on metal coordination and CO2 sorption behavior.

本实验旨在明确用于二氧化碳（CO₂）捕集的金属有机框架（Metal-Organic Framework, MOF）材料中过渡金属的分布特征与局域配位环境。本研究将考察一系列通式为(MI)₂(MII)₃(C₆H₄O₇)₂·2H₂O的碱金属-过渡金属柠檬酸二水合物，其中MI代表Li、Na、K，MII代表Fe、Co、Ni、Zn。实验起始组分为K₂Co₃(C₆H₄O₇)₂·2H₂O，其余金属将部分取代体系中的主体金属。

本实验将采用多功能气体反应器，在常温常压条件下，分别以非原位（ex situ）与原位（in situ）两种模式开展CO₂吸附实验。将在Fe、Co、Ni及Zn的K吸收边处采集X射线吸收近边结构（X-ray Absorption Near Edge Structure, XANES）与扩展X射线吸收精细结构（Extended X-ray Absorption Fine Structure, EXAFS）数据。根据可用实验时长，还将开展可控湿度环境下的补充原位实验，以评估水分对金属配位环境及CO₂捕集行为的影响。