[Fe3O4@CQD@Si(OEt)(CH2)3NH@CC@Ad@SO3H]+Cl−: As a new, efficient, magnetically separable and reusable heterogeneous solid acid catalyst for the synthesis of 5-amino-1,3-diphenyl-1H-pyrazole 4-carbonitril and pyrano[2,3-c] pyrazole derivatives

Magnetic nano-Fe3O4 based on adenine was synthesized with surface high-density functional group, namely SO3H, so that it is a novel Brønsted acid nanomagnetic catalyst, and acts as a solid heterogeneous catalyst. Also in this catalyst, the surface of the Fe3O4 nanoparticles was protected using carbon quantum dots (CQDs). The as-synthesized catalyst was characterized using different techniques, including Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy (EDX), energy-dispersive X-ray spectroscopy mapping (EDX mapping), vibrating sample magnetometer (VSM), thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). The activity of the as-synthesized catalyst was evaluated in the synthesis of 5-amino-1, 3-diphenyl-1H-pyrazole 4-carbonitril and pyrano[2,3-c] pyrazole derivatives. The proposed method has important features which include solvent-free, mild, metal-free, high yield, shorter reaction time, easy recovery of catalyst and easy workup procedure. The effect of temperature and the amount of the catalyst (optimum reaction condition) were determined using a systematic approach, namely the design of experiment (DoE).