Table 3.

Comparison of the catalytic activity of the MCM-41-APS-PMDA-NHSO₃H (1) with other catalysts.

Entry	Catalyst	Amount of catalyst loading	Solvent	Temp. (°C)	Time (min)	Yield (%)	References
1	PPF-SO3H	250 mg	EtOH	Reflux	480	81	73
2	PANI-FeCl3	200 mg	CH3CN	Reflux	1440	83	82
3	Fe3O4/PAA-SO3H	60 mg	Solvent-free	RT	120	90	83
4	H2SO4.Silica gel	30 mol ⁒(47 mg)	Solvent-free	60 °C	120	89	84
5	Zr(H2PO4)2	7 mol ⁒(20 mg)	Solvent-free	90 °C	60	92	85
6	MCM-41-APS-PMDA-NHSO3H	15 mg	Solvent-free	80 °C	35	96	This work