Visible-light-responsive covalent organic frameworks (COFs) as photocatalysts for metal-free organic reactions are highly desirable due to their structural controllability and molecular functionality. In this study, we describe the fabrication of an anthraquinone functionalized COF linked by β-ketoenamines (AQ-COF), which presents a noodle-like nanofiber structure with staggered AB stacking mode. The as-resultant AQ-COF was efficiently utilized as a metal-free heterogeneous catalyst for selective aerobic oxidation of sulfides under visible-light irradiation. Compared with the precedential AQ-COFDMF with spherical particles, the proposed AQ-COF presents a higher photocatalytic activity with high selectivity to sulfoxides and chemical stability. Further characterization techniques revealed that the unique morphology and structure can greatly enhance charge transfer and separation efficiency of photogenerated electron–hole pairs, thus giving rise to the improvement of photocatalytic activity.

Covalent triazine frameworks (CTFs) with donor–acceptor motifs have been identified as prospective semiconducting materials for photocatalysis. Though donor–acceptor motifs can favor forward intramolecular charge separation, some cases still suffer from backward charge recombination, resulting in the decrease of the photocatalytic activity. Herein, acetylene-bridged CTFs bearing an extended donor−π–acceptor motif was fabricated to prompt exciton dissociation. Experimental investigations and density functional theory calculations prove that the acetylene moiety can suppress backward charge recombination, minimize exciton binding energy, and enhance charge carrier lifetime, thereby prompting forward charge transfer/separation in comparison to the analogous one without acetylene. Thus, the acetylene-bridged CTFs showcased a higher photocatalytic activity for metal-free photocatalytic oxidative amines coupling with oxygen under visible-light irradiation, and apparent quantum efficiency at 420 nm was achieved up to 32.3%, that is, twofold higher than the one without acetylene. Furthermore, the acetylene moieties can adsorb oxygen molecules and provide active sites to lower the energy barrier and thus significantly enable the photoredox catalysis. This work provides alternative insights into the design and construction of high-performance CTFs, with prospective applications in solar-to-chemical energy conversion.

Covalent organic frameworks (COFs) are appealing platforms for photocatalysts because of their structural diversity and adjustable optical band gaps. The construction of efficient COFs for heterogeneous photocatalysis of organic transformations is highly desirable. Herein, we constructed a photoactive COF containing benzothiadiazole and triazine (BTDA−TAPT), for which the morphology and crystallinity might be easily tuned by slight synthetic variation. To unveil the relationship of photocatalytic properties between the structure and morphology, analogous COFs were synthesized by precisely tailoring building blocks. Systematic investigations indicated that tuning the structure and morphology might greatly impact photoelectric properties. The BTDA−TAPT featuring ordered alignment and perfect crystalline nature was more beneficial for promoting charge transfer and separation, which exhibited superior photocatalytic activity for visible light-driven oxidative coupling of amines. Outcomes from this study reveal the intrinsic synergy effects between the structure and morphology of COFs for photocatalysis.

This paper describes the fabrication of covalent triazine framework nanosheet-encapsulated Ag nanoparticles (Ag0@CTFN) via a simple combination of the ultrasonic exfoliation and solution infiltration method. The as-prepared Ag0@CTFN displays an order layered-sheet structure with abundant micropores and mesopores, whereas ultrafine Ag nanoparticles are confined and stabilized in their interlayers through the interaction between N sites of triazine units and Ag nanoparticles. Considering that the Ag0@CTFN possesses the merits of high nitrogen, low density, and abundant basic sites, it was thus believed to have enough abilities to adsorb and activate CO2 in the CO2 conversion and catalysis. Importantly, the Ag0@CTFN, as a heterogeneous catalyst, showed highly catalytic activity in the carboxylation of various alkynes with CO2 at ambient pressure and low temperature. This catalyst also exhibited good functional group tolerance and excellent stability without any significant loss of its activity after six recycles. This work not only achieves valuable and novel composite material but also provides the first application of covalent triazine framework nanosheets in chemical conversion of CO2, opening a new field in preparing recyclable heterogeneous catalysts to accelerate the utilization of CO2.

Photocatalytic CO 2 reduction holds great promise for synchronously addressing carbon neutrality and producing fuels, although enhancing the photocatalyst activity and tuning the product selectivity remain enormous challenges. Herein, we synthesized four crystalline and porous benzothiadiazole-based covalent organic frameworks (COFs) with different carbonyl groups and reported a dual metalation strategy to fabricate Co and Ni dual-metal sites anchored on the benzothiadiazole-based COFs by the interaction between metal and thiadiazole for highperformance CO 2 photoreduction. Among the as-synthesized COFs metalated by Co/Ni dual sites, CoNi−COF-3 achieved an impressive CO generation rate of 2567 μmol g −1 h −1 with a selectivity of 92.2%, which were significantly higher than those of single sites. Experimental and theoretical results revealed that the superior photocatalytic performance was attributed to the synergic effect of the fully β-ketoenamine-tautomerized COF-3 configuration and dual-metal sites, which not only facilitated the photogenerated charge carrier dynamics but also reduced the energy barriers of *COOH formation and promoted CO 2 adsorption and CO desorption. This work provides valuable insights into the future design of improved COF photocatalysts for highperformance CO 2 conversion.