A heterogeneous nickel-supported catalyst: a circular approach to amine synthesis via azide and nitro compound reduction

The development of sustainable catalytic methods is a crucial tool for advancing green chemistry and reducing its associated environmental impact. In this study, we present an eco-friendly approach for reducing azido and nitro compounds to their corresponding amines using a heterogeneous nickel-based catalyst supported on sulfonated biochar derived from pine needle (PiNe) valorisation. The system developed, in combination with the use of NaBH₄ as a safer reducing agent in water, enables efficient transformations under mild reaction conditions, yielding excellent results. The process also incorporates a green work-up procedure that employs bio-based, non-toxic solvents, such as 2-MeTHF, to aid in product isolation and catalyst recovery, thereby significantly reducing waste generation. Moreover, recycling studies demonstrate that Ni(B)/PiNe retains its catalytic efficiency for over five consecutive cycles. This work highlights the potential of biomass-derived materials in sustainable catalysis, demonstrating that green alternatives can be as effective as traditional methods while providing a protocol that aligns with the growing demand for environmentally friendly chemistry.