An Ethynyl-Linked sp-Carbon-Conjugated Covalent Organic Framework through Sonogashira Cross-Coupling Reactions

We report the synthesis of ethynyl-linked covalent organic frameworks through microinterfacial polymerization with Sonogashira cross-coupling reactions of 5,10,15,20-tetrakis(4-ethynylphenyl)porphyrin (TEPP) and 5,10,15,20-tetrakis(4-bromophenyl)porphyrin (TBPP). This framework consists of extended two-dimensional tetragonal layers with porphyrin knots and ethynyl (-C≡C-) linkers and constitutes layered frameworks with an AB-stacking mode, creating periodically ordered porphyrin arrays and one-dimensional microporous channels. The ethynyl-linked porphyrin framework features a broad absorption spectrum that covers the entire visible region and extends to the infrared zone exceeding 1400 nm, exhibits a low optical bandgap of 1.32 eV, and is photoconductive, generating prominent photocurrent. The micropores formed by the AB stacking are highly accessible, enabling iodine uptake, CO2 capture, and Li+ confinement. Remarkably, the Li+-confined frameworks exhibit Li+ conductivity of 2.1 × 10-5 S cm-1 at 100 °C under anhydrous conditions and achieve an exceptional Li+ conductivity of 3.9 × 10-3 S cm-1 at a relative humidity of 98%. Temperature-dependent experiments revealed that Li+ conduction is facilitated by a low-energy barrier hopping mechanism. We envision that our ethynyl linkage strategy will not only develop novel sp-carbon-conjugated frameworks but also enable unprecedented functions.