Hydrogen-Bonded Organic Framework Ultrathin Nanosheets for Efficient Visible-Light Photocatalytic CO 2 Reduction.

Post-modification of robust guanine-quadruplex-linked 2,2'-pyridine-containing HOF-25 with Ni(ClO 4 ) 2  ⋅ 6 H 2 O followed by exfoliation using sonication method affords hydrogen-bonded organic framework (HOF) nanosheets (NSs) of HOF-25-Ni in the yield of 56 %. TEM and AFM technologies disclose the ultrathin nature of HOF-25-Ni NSs with thickness of 4.4 nm. STM observation determines the presence of sql segments assembled from HOF-25-Ni building blocks at the heptanoic acid/highly oriented pyrolytic graphite interface, supporting the simulated 2D supramolecular framework. ICP-MS, XAS, and XPS data prove the successful immobilization of atomic nickel sites on the 20 % total 2,2'-pyridine moieties in crystalline HOF-25-Ni. With the aid of [Ru(bpy) 3 ] 2+ and triisopropanolamine, 10 wt% HOF-25-Ni NSs dispersed on graphene oxide efficiently promotes visible-light-driven CO 2 reduction, showing a 96.3 % CO selectivity with a prominent conversion rate up to 24 323 μmol g -1  h -1 .