Highly Selective Decarboxylative Dimerization via Molecular Self-Assembly-Induced Confinement Effects

On-surface synthesis of specified products with high selectivity represents a powerful approach to fabricate functional materials. The regulation of selectivity has always been a focal point of interest, and a diverse of methods are utilized to meticulously control the reaction process, thereby achieving high selectivity. This study investigates the selective decarboxylative coupling reactions of heptaazaphenalene-tribenzoic acid (HTBA) molecules on the Ag(111) surface. A pre-assembly strategy was employed to engineer a molecular template, steering the surface reaction exclusively toward HTBA dimerization, achieving a high selectivity of over 90%. The surface species throughout the reaction were monitored by STM, and in-situ heating STM experiments confirmed the thermal stability of the self-assembled structure, showing that it persists even at the reaction temperature. Control experiments using pseudo-high dilution to suppress molecular template effects underscore its decisive role in dictating both selectivity and efficiency. This study offers a benchmark for elucidating how molecular templates accelerate chemical transformations and for achieving decarboxylative coupling under mild, surface-confined conditions.