A metal-free photoactive nitrogen-doped carbon nanosolenoid with broad absorption in visible region for efficient photocatalysis

Riemann surfaces inspired chemists to design and synthesize such multidimensional curved carbon architectures. It has been predicted that carbon nanosolenoid materials with Riemann surfaces have unique structures and novel physical properties. Here we report the first synthesis of a nitrogen-doped carbon nanosolenoid (N-CNS) using bottom-up approach with a well-defined structure. N-CNS was obtained by a rational Suzuki polymerization, followed by oxidative cyclodehydrogenation. The successful synthesis of N-CNS was fully characterized by GPC, FTIR, solid-state 13C NMR and Raman techniques. The intrinsic single-strand molecular structures of N-CNS helices can be clearly resolved using low-dose integrated differential phase contrast scanning transmission electron microscopy (iDPC-STEM) technique. Possessing unique structural and physical properties, this long π-extended polymer N-CNS can provide new insight towards bottom-up syntheses of curved nanoribbons and potential applications as a metal-free photocatalyst for visible-light-driven H2 evolution and highly efficient photocatalyst for photoredox organic transformations.

Compound 3-7 and M1 were prepared according to the published procedures S1-S3 .

Synthesis of compound 4.
A mixture of tetrahydrofuran (20 mL), triethylamine (20 mL), 5-bromopyrimidine (5 g, 31.5 mmol), triphenylphosphine (0.366 g, 1.39 mmol), copper (I) idodide (1.06 g, 5.56 mmol), Bis(triphenylphosphine)palladium(II) dichloride was degased for 15 minutes with nitrogen gas bubbling through the system and ethynyl(trimethyl)silane was added to the reaction flask while degassing.The reaction mixture was heated to 60º C for 15 hours, then cooled down to room temperature, concentrated to dryness under reduced pressure and the resulted solid was washed with diethyl ether (2×50 mL) and dried under vacuum to get crude product compound 3 without further purification.Methanol (30 mL) and potassium carbonate (7.68 g, 55.6 mmol) were added to compound 3 and the reaction mixture was agitated at room temperature for 2 hours.The reaction mixture was concentrated to dryness under reduced pressure and the resulted solid was washed with ethyl acetate (2×50 mL) and dried under reduced pressure to obtain crude product compound 4 (3 g, 93% yield) and used without additional purification. 1H NMR (CDCl3, 400 MHz): δ 9.12 (s, 1H), 8.83 (s, 2H), 3.40 (s, 1H).
Synthesis of compound 6.Phenanthrene-9,10-dione (3.5 g, 16.8 mmol) was dissolved in 98% H2SO4 (190 mL) and N-Bromosuccinimide (6.4 g, 36.0 mmol) was added in portions over a period of 40 minutes with continuous stirring.The mixture was vigorously stirred at room temperature for 3 days, then the reaction mixture was poured into a large beaker containing crushed ice and left for 1 hour with stirring.The reaction product was filtered and washed thoroughly with water.The crude product was washed by DMSO to afford compound 6 as orange solid (5.0 g, 81%). 1
The resulting solution was then cooled to 0 °C and 1,2-dibromobenzene (4.00 g, 16.9 mmol) was added in one portion.The mixture was vigorously stirred at 0 °C for 4 hours, and then was poured into ice water.The resulting white precipitate was filtered off, washed with much water, dissolved in CHCl3 and washed with 10% NaHSO3 (aq.), dried over anhydrous MgSO4, and then concentrated by rotary evaporator.The crude product was purified by crystallization from CHCl3/hexanes to afforded compound 1 (6.7 g, 81%) as a white crystalline solid. 1 H NMR (CDCl3, 400 MHz): δ 8.05 (s, 2H).

Figure S7 .
Figure S7.(a) Helical structure of N-CNS with the removal of substituent group; (b) the scheme of lead angle.

Figure S10 .
Figure S10.H2 evolution rates under visible light and full spectrum light irradiation.

Figure S14 .
Figure S14.The absorption spectra of N-CNS before and after photocatalytic aza-Henry reaction.