A heteroleptic copper complex, Cu(bathocup)(XantPhos)BF₄ promotes the fragmentation of lignin models of the β-O-4 linkage under aqueous biphasic reaction conditions using catalytic amounts of NABnH, a hydrogen atom donor. The catalytic system as a whole represents a green shift from previous reaction conditions for analogous processes that exploit expensive rare metals such as Ir for photocatalysis, employ stoichiometric amounts of proton- and/or hydrogen (H) atom donors and chlorinated solvents. The reaction conditions and catalyst system are amendable to flow chemistry set-ups for gram scale fragmentation of lignin polymer models.