Synthesis of Vinylene-Linked Two-Dimensional Conjugated Polymers via the Horner-Wadsworth-Emmons Reaction

In this work, we demonstrate the first synthesis of vinylene-linked 2D CPs, namely, 2D poly(phenylenequinoxalinevinylene)s2D-PPQV1and2D-PPQV2, via the Horner-Wadsworth-Emmons (HWE) reaction ofC(2)-symmetric 1,4-bis(diethylphosphonomethyl)benzene or 4,4 '-bis(diethylphosphonomethyl)biphenyl withC(3)-symmetric 2,3,8,9,14,15-hexa(4-formylphenyl)diquinoxalino[2,3-a:2 ',3 '-c]phenazine as monomers. Density functional theory (DFT) simulations unveil the crucial role of the initial reversible C-C single bond formation for the synthesis of crystalline 2D CPs. Powder X-ray diffraction (PXRD) studies and nitrogen adsorption-desorption measurements demonstrate the formation of proclaimed crystalline, dual-pore structures with surface areas of up to 440 m(2) g(-1). More importantly, the optoelectronic properties of the obtained2D-PPQV1(E-g=2.2 eV) and2D-PPQV2(E-g=2.2 eV) are compared with those of cyano-vinylene-linked2D-CN-PPQV1(E-g=2.4 eV) produced by the Knoevenagel reaction and imine-linked 2D COF analog (2D-C=N-PPQV1, E-g=2.3 eV), unambiguously proving the superior conjugation of the vinylene-linked 2D CPs using the HWE reaction.