Low-temperature synthesis of cation-ordered bulk Zn3WN4 semiconductor via heterovalent solid-state metathesis

Metathesis reactions are widely used in synthetic chemistry. While state-of-the-art organic metathesis involves highly controlled processes where specific bonds are broken and formed, inorganic metathesis reactions are often extremely exothermic and, consequently, poorly controlled. Ternary nitrides offer a technologically relevant platform for expanding synthetic control of inorganic metathesis reactions. Here, we show that energy-controlled metathesis reactions involving a heterovalent exchange are possible in inorganic nitrides. We synthesized Zn3WN4 by swapping Zn2+ and Li+ between Li6WN4 and ZnX2 (X = Br, Cl, F) precursors. The in situ synchrotron powder X-ray diffraction and differential scanning calorimetry show that the reaction onset is correlated with the ZnX2 melting point and that product purity is inversely correlated with the reaction's exothermicity. Therefore, careful choice of the halide counterion (i.e., ZnBr2) allows the synthesis to proceed in a swift but controlled manner at a surprisingly low temperature for an inorganic nitride (300 °C). High resolution synchrotron powder X-ray diffraction and diffuse reflectance spectroscopy confirm the synthesis of a cation-ordered Zn3WN4 semiconducting material. We hypothesize that this synthesis strategy is generalizable because many Li–M–N phases are known (where M is a metal) and could therefore serve as precursors for metathesis reactions targeting new ternary nitrides. This work expands the synthetic control of inorganic metathesis reactions in a way that will accelerate the discovery of novel functional ternary nitrides and other currently inaccessible materials.