Fabrication of NiFe layered double hydroxides using urea hydrolysis—Control of interlayer anion and investigation on their catalytic performance

• NiFe–NO3-LDH, Ni(HCO3)2 and NiFe–CO3-LDH shiftingly appeared in NiFe-LDH synthesis.
• Reasons for this shifting were investigated by monitoring the pH value.
• Catalytic performances of NiFe–NO3-LDH and NiFe–CO3-LDH were evaluated.
• The different catalytic results were analyzed based on acid catalysis theory.
• Catalytic mechanism of benzoin ethyl ether synthesis with NiFe-LDHs was studied.

NiFe layered double hydroxides (NiFe-LDHs) intercalated with nitrate and carbonate anion were synthesized by urea hydrolysis. The aging time and the molar ratio of NO3−/urea were varied in order to identify suitable parameters, which control the interlayer anion (nitrate or carbonate) and crystal structure of the final products. The prepared samples were applied to the one-pot synthesis of benzoin ethyl ether from benzaldehyde and ethanol. NiFe–NO3-LDH presented excellent catalytic activity, different from NiFe–CO3-LDH which showed none catalytic activity at all.

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