A metal-decorated alkene-linked covalent organic framework is a robust, selective photocatalyst for CO2 reduction.

The synthesis of three-dimensional (3D) covalent organic frameworks (COFs) requires high-connectivity polyhedral building blocks or the controlled alignment of building blocks. Here, we use the latter strategy to assemble square-planar cobalt­(II) phthalocyanine (PcCo) units into the nbo topology by using tetrahedral spiroborate (SPB) linkages that were chosen to provide the necessary 90° dihedral angles between neighboring PcCo units. This yields a porous 3D COF, SPB-COF-DBA, with a noninterpenetrated nbo topology. SPB-COF-DBA shows high crystallinity and long-range order, with 11 resolved diffraction peaks in the experimental powder X-ray diffraction (PXRD) pattern. This well-ordered crystal lattice can also be imaged by using high-resolution transmission electron microscopy (HR-TEM). SPB-COF-DBA has cubic pores and exhibits permanent porosity with a Brunauer–Emmett–Teller (BET) surface area of 1726 m2 g–1.

Covalent organic framework nanosheets (CONs), fabricated from two dimensional covalent organic frameworks (COFs), present a promising strategy for incorporating atomically distributed catalytic metal centers into welldefined pore structures with desirable chemical environments. Here, a series of CONs was synthesized embedding single cobalt sites that were then evaluated for photocatalytic carbon dioxide reduction. A partially fluorinated, cobalt-loaded CON produced 10.1 µmol carbon monoxide with a selectivity of 76%, over 6 hours irradiation under visible light (turnover number = 28.1) and a high external quantum efficiency of 6.6% under 420 nm irradiation in the presence of an iridium dye. The CONs appear to act as a semiconducting support, facilitating charge-carrier transfer between the dye and the cobalt centers, and this results in a performance comparable with the state-of-the-art heterogeneous catalysts in the literature under similar conditions. The ultra-thin CONs outperformed their bulk counterparts in all cases, suggesting a general strategy to enhance the photocatalytic activities of COF materials.

A range of linear conjugated polymers is reported that promote simultaneous photocatalytic CO2 reduction and proton reduction with a sacrificial hole-scavenger.

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