Cumulene-Based Conjugated Microporous Polymers

Low-dimensional C(sp)-rich conjugated microporous polymers, including graph(di)ynes, have fascinated chemists due to their unique material properties and expeditious synthesis. While all existing examples are based on acetylene units, their ground-state quinoidal counterparts featuring cumulene linkages have surprisingly remained unexplored. Here, we report an interfacial condensation polymerization of trifunctional propargylic electrophiles (iCPPE), enabling the bottom-up assembly of [5]cumulene-linked conjugated microporous polymers ([5]C-CMPs). This method yields centimeter-scale, free-standing thin films that can be exfoliated into ~10 nm thick nanosheets. The rigid framework stabilizes the cumulene moieties, resulting in high porosity (specific surface area up to 486.3 m2/g), a narrow bandgap (1.32 eV), and a triplet ground state, which stand in sharp contrast to those of their alkyne-based analogues. Benefiting from their open-shell character and fast non-radiative relaxation, [5]C-CMPs achieve a photothermal conversion efficiency of up to 75%. This work establishes a distinct redox-neutral strategy for constructing lowdimensional carbon-rich materials with unique optoelectronic and magnetic properties.