Modification of Cu–ZnO–ZrO2 catalysts with La2O3 to quantitatively tune Cu+–Cu0 dual sites for hydrogenation of dimethyl adipate to produce 1,6-hexanediol

The strong electron donor–acceptor interaction between lanthanum and copper species retards the aggregation of the copper species, and inhibits the transformation of Cu 2 O to metallic Cu, thus maintaining a constant ratio of Cu + /(Cu 0 + Cu + ).