Photoisomerization-mediated tunable pore size in metal organic frameworks for U(VI)/V(V) selective separation
Pengcheng Zhang, Yixin Zhang, Fei Wu, Weixiang Xiao, Weiwei Hua, Ziwen Tang, Wei Liu, Suwen Chen, Yaxing Wang, Wangsuo Wu, Duoqiang Pan
Abstract
Selective extracting uranium from seawater is quite challenging, particularly the presence of vanadium, which poses a significant obstacle for most amidoxime absorbents. Adsorbents with size-matched pores and coordination environment can improve the uranium selectivity but usually deteriorate the adsorption capacity. Herein, a dynamically matched spatial coordination strategy is proposed to improve the performance of uranium extraction. The diarylethene (DAE) photoswitch with photoisomerization characteristic is introduced into Metal-Organic Frameworks (MOFs), in which the tunable pore size and coordination environment provide a precisely confined space for uranium capture under the dynamic adjustment of ultraviolet-visible (UV-Vis) irradiation. Proposed material with photo-responsive gated rectification capability can effectively extract uranium from vanadium-rich system, the uranium adsorption capacity reaches 588.24 mg·g−1 and the U(VI)/V(V) separation factor ratio is recorded up to 215. Finite element simulation confirms the enhancement of mass transfer under the open-state of DAE, which leads to the improved adsorption capacity. Density Functional Theory (DFT) calculations suggest size-matching between pore structure and uranium species, as well as the spatial coordination between the closed-state DAE and uranium species, results in the U(VI)/V(V) selectivity and uranium extraction performance. Current work presents a promising strategy for improving the uranium extraction ability and U(VI)/V(V) selectivity under seawater environment. Selectively extracting U(VI) from seawater is challenging. Here, authors propose a dynamically matched spatial coordination strategy to improve the extraction of U(VI). With the size-matching and the spatial coordination, uranium species are precisely captured in confined coordination space.