Construction of Bimetallic Metal–Organic Frameworks with the Nanosheet-Assembled Hierarchical Hollow Structure for CO₂ Fixation

Abstract

Incorporating secondary metal nodes with functionality into organic ligand nodes to form a bimetallic metal-organic frameworks (MOFs) would facilitate an enhancement in properties and broaden applied areas of MOFs. Hierarchical tubular Cu/Zn-MOF-74 assembled by nanosheet arrays is synthesized at ambient temperature and pressure by phase transformation of Cu-based precursor MOF in immersion solution with Zn²⁺. The content of Zn in Cu/Zn-MOF-74 can be controlled by adjusting the concentration of Zn²⁺ in immersion solution, and it can reach a maximum of 36.4%. Moreover, the catalytic activity toward cycloaddition of CO₂ with styrene oxide of Cu/Zn-MOF-74 is improved significantly compared with that of monometallic Cu-MOF-74. Meanwhile, the advanced hierarchical tubular structure contributing to enhancement in catalytic activity enables Cu/Zn-MOF-74 to present higher conversion toward this cycloaddition of CO₂ than traditional rod-like Cu/Zn-MOF-74. This templated synthesis would provide an opportunity for designing various bimetallic MOFs or MOF-based compounds with improved performances in multiple applications.