Juan Wang

Photocatalytic CO2 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 high-performance CO2 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 CO2 adsorption and CO desorption. This work provides valuable insights into the future design of improved COF photocatalysts for high-performance CO2 conversion.

Abstract Metal nanoclusters have recently attracted extensive interest not only for fundamental scientific research, but also for practical applications. For fundamental scientific research, it is of major importance to explore the internal structure and crystallographic arrangement. Herein, we synthesize a gold nanocluster whose composition is determined to be Au 60 S 6 (SCH 2 Ph) 36 by using electrospray ionization mass spectrometry and single crystal X-ray crystallography (SCXC). SCXC also reveals that Au 60 S 6 (SCH 2 Ph) 36 consists of a fcc-like Au 20 kernel protected by a pair of giant Au 20 S 3 (SCH 2 Ph) 18 staple motifs, which contain 6 tetrahedral-coordinate μ 4 -S atoms not previously reported in the Au–S interface. Importantly, the fourth crystallographic closest-packed pattern, termed 6H left-handed helical (6HLH) arrangement, which results in the distinct loss of solid photoluminescence of amorphous Au 60 S 6 (SCH 2 Ph) 36 , is found in the crystals of Au 60 S 6 (SCH 2 Ph) 36 . The solvent-polarity-dependent solution photoluminescence is also demonstrated. Overall, this work provides important insights about the structure, Au–S bonding and solid photoluminescence of gold nanoclusters.

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.

Photocatalytic CO2 reduction into CH4 is an appealing approach to alleviate the current energy and environmental crisis; however, achieving high selectivity and conversion efficiency still remains challenging. The rational design of photocatalysts for CO2 adsorption and activation is thus crucial. Here, we designed and synthesized two redox-active truxene-based conjugated microporous polymers linked by thiazolo[5,4-d]thiazole for metal-free photocatalytic reduction of CO2 to CH4. Significantly, the optimized polymer with the extended π-conjugated system, denoted Tx-TzTz-CMP-2, presented a higher CH4 production rate of 300.6 μmol g–1 h–1 with a selectivity of 71.2% without any metal cocatalyst and photosensitizer, which outperformed most of the previously reported photocatalysts. Experimental and theoretical investigations revealed that introducing phenyl as a π-bridge extending electron delocalization of conjugated system might effectively minimize exciton binding energy, thereby boosting the intramolecular charge transfer and separation abilities. Meanwhile, the N-site of the thiazole unit acted as an electron reservoir and a catalytic center for activating the adsorbed CO2 and forming CH4 by subsequent hydrogenation. This work highlights the significance of the extended π-conjugated system in metal-free conjugated microporous polymers to improve the activity and selectivity of CO2 photoreduction to CH4.

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.