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.