Mesoporous Carbon of Carbonized Human Urine Waste: A Valuable Heterogeneous Catalyst for Chromene and Xanthene Derivative Synthesis

Human urine is universal unused waste material that is regularly disposed of by the human body. We, for the first time, presented an economically beneficial, sustainable, and novel route to synthesize mesoporous human urine carbon (HUC)-containing heteroatoms, i.e., C, Na, Cl, N, S, and P, using a human urine waste. The as-synthesized HUC were envisaged for their structural elucidation, morphology evolution, crystal structure, functional bonding, and elemental composition analyses through various sophisticated technologies. The HUC catalyst had a moderately crystalline nature due to the graphitic phase of carbon with a particle size of 20-50 nm, which was successfully used to synthesizing chromenes, 1,8-di-oxo-octahydroxanthenes, and benzypyrazolylcoumarin and biscoumarin derivatives through a one-pot multicomponent reaction with 20 mg of catalyst in EtOH/H2O solvent. This eco-friendly and simple method offers numerous advantages such as easy purification, clean reaction, and excellent yield for organic synthesis. The HUC catalyst can be recycled ten times and reused multiple times after activation without affecting catalytic performance.