Rational Synthesis of Isomeric Graphdiyne Frameworks toward Single-Ruthenium Catalysts and High-Performance Nitrogen Reduction

Abstract

Graphdiynes (GDYs), synthesized via direct coupling of arylacetylenes, have attracted great attention due to their unique electronic properties and structural diversity, typically forming 2D layered frameworks. However, crystalline GDY-like frameworks with 3D topology remain challenging to synthesize. Here, the study reports two highly crystalline, isomeric GDY-like frameworks with ThSi2 topology, constructed from 2,2′-binaphthalene and 6,6′-biazulene-based monomers. The azulene-based framework, due to its large dipole moment, exhibits a narrow bandgap of 1.15 eV, significantly lower than its naphthalene counterpart (2.33 eV). As ruthenium (Ru) single-atom supports, these frameworks enable strong Ru-diyne interactions, achieving an ammonia yield rate of 188.7 ± 1.6 µg h⁻¹ mg_cat⁻¹ and a Faradaic efficiency of 37.4 ± 0.6%. Such bicontinuous channels and tunable electronic structures offer electrocatalysis field new opportunities. Moreover, the azulene-based framework, featuring a higher highest occupied molecular orbital and lower lowest unoccupied molecular orbital energy level, ensures superior electron mobility. These 3D crystalline frameworks introduce a new covalent organic framework (COF) family with diyne linkages and pure carbon skeletons, broadening the scope of COF materials. Their well-defined structures provide an ideal platform for tuning optoelectronic properties, enabling fundamental studies on structure-property relationships and opening new opportunities for catalytic and electronic applications.