A comparison of the catalytic activity of the (Fe₃O₄@NFC@NSalophCu)CO₂H catalyst with some reported catalysts for 5-substituted-1H-tetrazole multi-component reactions.

Reaction	Catalyst	Reaction conditions	Time (h)	Yielda (%)	Ref.
5-Substituted-1H-tetrazoleb	CuNO3·3H2O	DMSO/120 °C	24	78	65
	Nano-Cu2O-MFR	DMF/100 °C	8	92	66
	Cu–MCM-41	DMF/140 °C	12	90	67
	Copper(ii) Schiff base	DMF/110 °C	7	91	53
	Bi(OTf)3	DMF/120 °C	24	87	68
	Cu(OAC)2	DMF/120 °C	12	96	69
	(NH4)4Ce(SO4)4–2H2O	DMF/reflux	5	72	70
	Humic acid	H2O/100 °C	4	92	71
	Fe3O4–CNT–TEA–Cu(ii)	DMF/70 °C	1.5	96	54
	(Fe3O4@NFC@NSalophCu)CO2H	H2O/60 °C	0.25	97	This work

^aIsolated yield.

^bReaction conditions: benzaldehyde (1.0 mmol), hydroxylamine (1.2 mmol), and sodium azide (1.5 mmol).