Phosphoric acid-mediated 3D honeycomb-structured g-C3N4 as a high-performance support for ultrafine Pt nanoparticles in phenol hydrogenation

This work introduces a template-free strategy for preparing three-dimensional (3D) honeycomb-like graphitic carbon nitride (g-C 3 N 4 ) with high specific surface area through phosphoric acid-regulated supramolecular self-assembly. By systematically tuning phosphoric acid dosage, the self-assembly process of melamine-cyanuric acid aggregates is precisely controlled, resulting in a hierarchically porous architecture with interconnected channels and abundant porosity. The optimized phosphoric acid-mediated support (SSCN-0.89) enables uniform dispersion and stabilization of ultrafine Pt nanoparticles (∼1.7 nm) via enhanced metal-support interactions. Under mild conditions (120 ℃, 0.5 MPa H 2 ), the resultant Pt/SSCN-0.89 catalyst achieves 94.1 % phenol conversion within 80 min with exclusive cyclohexanol selectivity (100 %). Mechanistic studies reveal that the hierarchical porous structure facilitates rapid mass transfer, while the tailored surface nitrogen species lower the reaction energy barrier. The catalyst retains robust stability over five cycles, demonstrating the pivotal role of 3D morphological engineering in designing high-performance carbon nitride-based catalytic supports for biomass upgrading.