Fig. 3From: Triphenylphosphine-based functional porous polymer as an efficient heterogeneous catalyst for the synthesis of cyclic carbonates from CO2 a Wide XPS spectrum, b Br spectrum, c N spectrum, and d P spectrum of TPDB-BP-TEA. The wide XPS spectra in Fig. 3 indicate the presence of P, C, N, Br, and O elements on TPDB-BP-TEABack to article page