Nanochannel-based heterometallic {ZnIIHoIII}-organic framework with high catalytic activity for the chemical fixation of CO2

Abstract

The exquisite combination of Zn^II and Ho^III generated the highly robust [ZnHo(CO₂)₆(OH₂)]-based heterometallic framework of {[ZnHo(TDP)(H₂O)]·5H₂O·3DMF} _n (NUC-30, H₆TDP = 2,4,6-tri(2',4'-dicarboxyphenyl)pyridine), which featured outstanding physicochemical properties, including honeycomb nanochannels, high porosity, large specific surface area, the coexistence of highly open Lewis acid-base sites, good thermal and chemical stability, and resistance to most organic solvents. Due to its extremely unsaturated metal tetra-coordinated Zn(ii) ions, hepta-coordinated Ho(iii) and high faveolate void volume (61.3%), the conversion rate of styrene oxide and CO₂ into cyclic carbonates in the presence of 2 mol% activated NUC-30 and 5 mol% n-Bu₄NBr reached 99% under the mild conditions of 1.0 MPa and 60 °C. Furthermore, the luminescence sensing experiments proved that NUC-30 could be used as a fast, sensitive and highly efficiency sensor for the detection of Fe³⁺ in aqueous solution. Therefore, these results prove that nanoporous MOFs assembled from pyridine-containing polycarboxylate ligands have wide applications, such as catalysis and as luminescent materials.