Facet Engineering-Modulated Electrochemiluminescence of Reticular Crystalline Nanoemitters

Electrochemiluminescence (ECL) as a light-emitting process involves the interfacial charge transfer between the electrochemically generated emitter's intermediate and the coreactant/emitter, critically governed by the emitter's electronic structure and exposed surface state. However, the relationship between the emitter's exposed surface state and ECL performance remains unexplored. Herein, a series of metal-organic framework (MOF) emitters is synthesized via controlled crystal growth, achieving selective exposure of (001), (100), and (110) facets characterized by micro-electron diffraction (MicroED) on nanoplate, nanoblock, and nanorod-shaped MOFs, respectively. Compared to (001) facet, the (110) and (100) facets exhibit 19.5 and 2.4-fold enhancement of ECL intensity, pronouncing facet-dependent ECL performance. Notably, the (110) facets exhibit 1088-fold ECL self-amplification due to the accumulation of stabilized radicals. Density functional theory calculations identify that the coreactant peroxydisulfate's lateral coordination with Zn(II) on the (110) facet strengthens chemisorption, elongates the O─O bond, and promotes its cleavage to form SO₄ ^•- radicals, thereby facilitating interfacial charge transfer to generate more excited states for ECL emission. The facet engineering provides a mechanistic guideline for designing crystalline ECL nanoemitters and decoding the fundamentals of ECL techniques.