Construction of Modifiable Phthalocyanine-Based Covalent Organic Frameworks with Irreversible Linking for Efficient Photocatalytic CO2 Reduction

TL;DR

Scientists created stable, modifiable COFs for efficient CO2 reduction using irreversible covalent bonds and optimized electron transfer.

Contribution

A new class of modifiable phthalocyanine-based COFs with irreversible covalent bonds for enhanced photocatalytic CO2 reduction.

Findings

CoBOP achieved record syngas production rates in photocatalytic CO2 reduction.

The linking unit enhances electron transfer efficiency between photosensitizer and active sites.

The COFs show exceptional stability in harsh thermal, acidic, and organic environments.

Abstract

Phthalocyanine-based covalent organic frameworks photocatalysts (CoOP, CoPOP, and CoBOP) with irreversible covalent linking were synthesized by designing bis-phthalonitrile precursors, exhibiting exceptional stability in thermal, acidic, alkaline, and organic environments.Tuning the conjugation length of the linking unit effectively modulates the electronic features of the photocatalyst.The linking unit serves as a ‘ladder’ between excited [Ru(bpy)3]Cl2 and Co2+, allowing the electrons to cascade down and facilitating rapid transfer, which is responsible for the excellent photocatalytic CO2 reduction reaction performance of the photocatalysts.

Phthalocyanine-based covalent organic frameworks photocatalysts (CoOP, CoPOP, and CoBOP) with irreversible covalent linking were synthesized by designing bis-phthalonitrile precursors, exhibiting exceptional stability in thermal, acidic, alkaline, and organic environments.

Tuning the conjugation length of the linking unit effectively modulates the electronic features of the photocatalyst.

The linking unit serves as a ‘ladder’ between excited [Ru(bpy)3]Cl2 and Co2+, allowing the electrons to cascade down and facilitating rapid transfer, which is responsible for the excellent photocatalytic CO2 reduction reaction performance of the photocatalysts.

The online version contains supplementary material available at 10.1007/s40820-025-01967-y.

Covalent organic frameworks (COFs) are considered promising catalysts for photocatalytic CO2 reduction reaction (pCO2RR) due to facilitated regulations. However, the instability of COFs with dynamic reversible covalent bonds and the limited modifiability of COFs with irreversible covalent bonds restricted the enhancement of the pCO2RR performance. Herein, three phthalocyanine-based COFs with ether-linked, CoOP, CoPOP, and CoBOP, were successfully prepared via in situ polycondensation using modifiable bis-phthalonitrile. CoBOP achieved a record of syngas performance in pCO2RR systems with photosensitizers and sacrificial agents (CO 83.7 mmol g−1 h−1 and H2 54.7 mmol g−1 h−1), surpassing most COF photocatalysts. Additionally, CoOP, CoPOP, and CoBOP exhibit stabilities in extreme environments owing to their irreversible covalent bonds. Experimental and density functional theory analyses confirm that the optimally matched the lowest unoccupied molecular orbital of the linking unit between the photosensitizer and active unit endowed CoBOP with the highest photoelectron transfer efficiency among the three catalysts, boosting its pCO2RR activity. This work is highly instructive for designing COFs with structure-adjustable and irreversible covalent bonds.

The online version contains supplementary material available at 10.1007/s40820-025-01967-y.

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