Abstract
Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, Sg-CN, which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature.
Highlights
Sulfonation of graphitic carbon nitride (g-CN) affords a polar and strongly acidic catalyst, sulfonated graphitic carbon nitride (Sg-CN), which displays unprecedented reactivity and selectivity in biodiesel synthesis and esterification reactions at room temperature
Engaged in the development of sustainable methods and converting waste products into valuable chemicals[30,31,32,33,34], we report the use of sulfonated graphitic carbon nitride (Sg-CN) as a benign and cost effective organo-sulfonated heterogeneous acid catalyst for the synthesis of biodiesel
Complete conversion of oleic acid to methyl oleate was discerned again (Table 1, entries 2–4) whereas the reaction with 10 mg of Sg-CN required overnight stirring for the completion of esterification at room temperature
Summary
The Sulfonated graphitic carbon nitride (Sg-CN) has been designed and synthesized via sequential calcination[33,34,35] and sulfonation of urea (Fig. 1). The SEM analysis clearly indicates the incorporation of sulfonic group in the graphitic carbon nitride framework; change in morphology of g-CN after sulfonation was discerned (Fig. 2). Juxtapose of FT-IR and 13C-NMR spectra of g-CN and Sg-CN corroborate the presence of essential functionality differences and electronic nature (See Supplementary) as evidenced by the peak at 1200 cm−1 a characteristic signal for sulfonated graphitic carbon nitride (see Supplementary, Fig. S4) which is confirmed by comparative analysis of 13C-NMR of g-CN and Sg-CN (see Supplementary, Fig. S5) The BET surface analysis of g-CN (35.42 m2/g, see Supplementary, Fig. S5 and Fig. S6) and Sg-CN (10.04 m2/g, see Supplementary, Fig. S7 and Fig. S8) confirmed the immobilization of sulfonic group. There is sharp decline in the surface area after the immobilization which is may be due to the creation of ionic character on the nitrogenous framework of g-CN culminating in the better interlayer attraction in graphitic carbon nitride
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