Fig. 3: Confirmation for formation of Cu(I) site in various NiCu-MOF-74 samples.
From: Major-auxiliary cooperative metal pairs in MOFs enable cascade oxidation of KA oil to ε-caprolactone
a Ultraviolet-visible spectroscopy recording possible reduction of Cu(II) ions by ethanol (EtOH), 2,5-dihydroxylterephthalic acid (DHTA) and N,N-dimethylformamide (DMF). FTIR spectra of MOF-74 samples and pristine 2,5-dihydroxyterephthalic acid in the range of b 4000–700 cm−1, c 3530–3050 cm−1, and d 1800−1500 cm−1. Note that ν and δ represent stretching vibration and bending vibration, respectively. e Periodic models of MOF-74 containing Cu(II)-Ni(II) pairs (left part) and Cu(I)-Ni(II) pairs (right part).
