An efficient and chemoselective mechanochemical synthesis of a bright TADF-emitting CuI-based compound is reported. The reaction of 2-(ethylsulfanyl)-6-methylpyridine (L) with CuI under solvent-free conditions or in solution results in a non-emissive complex, [Cu 2 I 2 L 2 ] (1) or a 1-D coordination polymer (CP), [Cu 3 I 3 L 2 ] n (CP 2), respectively. Meanwhile, the simple manual grinding of the reactants in the presence of a few drops of MeCN for 1-2 min chemoselectively gives the structurally different 1-D CP, [Cu 3 I 3 L 2 ] n (CP 3), as a single product isolated in 87% yield. Remarkably, both complex 1 and CP 2 under the mechanochemical conditions easily (1-2 min) undergo polymerization or isomerisation, accordingly, to afford CP 3. The structure of the latter is formed by cuprophilic interaction-free (-Cu-I-) n chains ligated by 2-(ethylsulfanyl)-6-methylpyridines in a μ 2 -N,S manner. At room temperature, CP 1 exhibits highly efficient blue-green TADF with a short lifetime (4.0 μs) and a high photoluminescence performance (PLQY being 70%).