Polypyridyl Coordination Motifs as Precursors for Ordered Carbonaceous Frameworks Toward High-Density Ru Single-Atom Catalysts.

Achieving high-density single-atom catalysts (SACs) remains a fundamental challenge, particularly for precious metals such as Ru that readily aggregate under synthetic and catalytic conditions. Here, we report a rational precursor design strategy for fabricating high-density Ru SACs via direct carbonization, yielding ordered carbonaceous frameworks (Ru-OCFs) with high Ru loadings of up to 11.0 wt%. By expanding the scope of precursors for OCF synthesis beyond conventional macrocyclic coordination motifs to coordinatively flexible polypyridyl ligands, we show that Ru-terpyridine crystals with thermally polymerizable ethynyl units serve as effective precursors for immobilizing single-atomic Ru species within three-dimensional porous carbon frameworks, without metal aggregation or post-synthetic treatments. The resulting Ru-OCFs retain the ordered structure and coordination environment of the precursor crystals while simultaneously developing microporosity with high specific surface areas of up to 670 m2 g-1. As a proof of concept, the high-density isolated Ru sites in Ru-OCFs enable enhanced catalytic activity in liquid-phase CO2 hydrogenation, achieving a high formic acid productivity of up to 19 mmol gcat -1 h-1, outperforming representative nanoparticle catalysts.