Figure 2

Spectra of the covalent organic frameworks obtained by the in-droplet approach at 100 °C for 15 min reactions. (a) ATR-IR spectra clearly indicating the absence of the organic building units and oligomers; the y axis is %transmittance; (b) 13C cross-polarization magic angle spinning solid-state nuclear magnetic resonance spectra displaying the characteristic β-keto peaks at ~180 p.p.m.