Triangular-Tessellated Charge Transfer Cocrystals Derived from Melamine with Enhanced Photocatalytic Performance

Charge transfer (CT) cocrystals hold great promise for advanced functional materials, yet controlling their CT interactions in terms of both structural design and precise synthesis remains challenging. Herein, a tessellation-based strategy to modulate CT strength in melamine-derived cocrystals is demonstrated, specifically in MMC-12 (melem:melamine = 1:2) and MMC-31 (3:1). Transient absorption (TA) spectroscopy and theoretical simulations reveal that MMC-31 exhibits enhanced CT interactions, facilitating rapid electron transfer from melamine to melem and forming weakly bound CT excitons. These excitons dissociate readily into free carriers, leading to an 18-fold enhancement in H₂O₂ production and a 12-fold enhancement in H₂ evolution compared to pristine melem. This work underscores the potential of geometric tessellation as a general design principle for high-performance organic semiconductors and photocatalysts.