Tailoring Edge Sites of B‑Doped g‑C₃N₄ To Promote Edge-Enriched Amine Functionalities for Enhanced CO₂ Cycloaddition

The utilization of CO₂ gas is highly valuable for cyclic carbonates. A boron-doped carbon nitride (BPCN-NH₂) material functionalized with edge-enriched -NH₂ groups was developed for efficient CO₂ cycloaddition to synthesize cyclic carbonates. B-doped graphitic carbon nitride (BPCN) was first prepared using NaBH₄ as the boron source, and was subsequently subjected to in situ hydrolysis. This second step constructed a nitrogen-rich microenvironment and endowed the material with edge-enriched amine (-NH₂) functional groups, leading to a 0.58% increase in their atomic content by XPS analysis. This design integrated boron doping and -NH₂ functionalization within the CN framework, synergistically enhancing CO₂ adsorption and activation through dual active sites. The BPCN-NH₂-1 catalyst demonstrated remarkable performance (99% yield, 99.0% selectivity) under specific conditions (110 °C, 1 MPa, 50 mg catalyst, 12 h). This superior efficiency is attributed to the synergistic interplay between the Lewis acidic boron dopant and the hydrogen-bond-donating amine moieties. Specifically, the boron centers act as Lewis acids, effectively activating the epoxide substrates toward nucleophilic attack. Concurrently, the amine groups, acting as basic hydrogen bond donors, facilitate the adsorption and activation of CO₂, thereby promoting the formation of key carbamate intermediates. This boron-nitrogen hybrid with amine functionalities provides a robust, recyclable platform for greener chemical synthesis.