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Abstract: Covalent organic frameworks (COFs) are emerging as a class of photocatalyst for solar energy utilization. The separation of photogenerated excitons in COFs is crucial for their photocatalytic performance. Herein, we report a strategy to tune the electronic structure of COFs by implanting Zn ions within the framework to facilitate the separation and utilization of the photoinduced charges. Zn ions are incorporated within the shell of hollow COF cages (Zn@H‐TpPa) by a sacrificial template method with a formation of hollow cages. The implantation of Zn ions within the framework results in a redistribution of electron density and an increment of the polarity of the COF, as evidenced by experimental and computational analyses, and thus contributes to the separation and transport of charge carries. The Zn@H‐TpPa shows enhanced photocatalytic H2 production efficiency as compared to TpPa. The results demonstrate a new way to optimize the electronic structure of COFs for photocatalysis. [ABSTRACT FROM AUTHOR]

Crystalline covalent organic frameworks (COFs) are porous polymeric semiconductors with network topologies, which are built from the integration of selected organic blocks with covalent bond linkages. They have shown great promise for artificial photosynthesis, owing to broad light harvesting, high crystallinity, and high carrier mobility. This Minireview introduces state‐of‐the‐art COF photocatalysts based on different linkages and discusses the origin of photocatalytic activities for hydrogen evolution. Three typical COF photocatalysts, with linkages including imine (−C=N−), β‐ketoenamine (O=C−C=C−NH−), and vinylene (−C=C−), are discussed with a particular focus on the advancements in synthetic methodologies and structural design, as well as photoelectronic properties that are relevant to photocatalytic performance. The Minireview is expected to elucidate their structure–property relationships and the way to design photoactive COFs with enhanced performances. [ABSTRACT FROM AUTHOR]

Photocatalytic CO2 reduction into carbonaceous feedstock chemicals is a promising renewable energy technology to convert solar energy and greenhouse gases into chemical fuels. Here, a covalent triazine‐based framework (CTF) is demonstrated as an efficient cocatalyst to reduce CO2 under visible‐light irradiation. The nitrogen‐rich triazine moieties in CTF contribute to CO2 adsorption, while the periodical pore structure of CTF favors the accommodation of CO2 and electron mediator. Immobilization of cobalt species onto CTF promotes the photocatalytic activity with a 44‐fold enhancement over pristine CTF and the optimal CO production rate of the obtained Co/CTFs was up to 50 μmol g−1 h−1. The results of solid‐state UV‐vis diffuse reflectance spectra (UV‐vis DRS), CO2 adsorption and electrochemical impedance spectroscopy (EIS) illustrated that the increased activity was ascribed to the enhanced CO2 capture capacity, improved absorption of visible‐light and facilitated the transfer of charge from CTF to CO2 molecules. The CTF not only serves as a substrate for active Co species, but also bridges the photosensitizer with cobalt catalytic sites for the efficient transfer of photoexcited electrons. This work highlights the capability and ease of fabricating covalent organic framework‐based photocatalytic systems that are potentially useful for energy‐conversion applications. [ABSTRACT FROM AUTHOR]

Development of visible-light-induced and rapid water disinfection is of significant importance. Covalent triazine-based frameworks (CTFs) with pre-designable structures and favorable semiconductive behaviors hold great promise for photocatalytic water disinfection. Here, we report an Ag/AgBr/CTF composite with a layered structure, which serves as an efficient photocatalyst for rapid water disinfection. Water disinfection with ＞99.99% inactivation of Escherichia coli within 12 min was achieved by using a small amount of Ag/AgBr/CTF under visible light irradiation. The inactivation efficiency of Ag/AgBr/CTF was ∼10 times better than that of bare Ag/AgBr. Rapid water disinfection by the Ag/AgBr/CTF composite mainly results from the greatly improved generation of reactive oxygen species through the synergistic effects among the three components and the affinity of CTF to the cell wall of bacteria. [ABSTRACT FROM AUTHOR]

Abstract: MoS2 quantum dots (QDs)‐modified covalent triazine‐based framework (MoS2/CTF) composites are synthesized through an in situ photodeposition method. MoS2 QDs are well distributed and stabilized on the layers of CTFs by coordination of the frameworks to MoS2. The QDs–sheet interactions between MoS2 and CTFs facilitate interfacial charge transfer and separation. As a consequence, the composites exhibit outstanding photocatalytic activity and stability for hydrogen evolution under visible light irradiation (λ≥420 nm), that exceed those over pristine CTFs and MoS2‐modified g‐C3N4 (MoS2/g‐C3N4) composite, making them promising materials for solar energy conversion. [ABSTRACT FROM AUTHOR]

Covalent triazine-based frameworks (CTFs) with a graphene-like layered morphology have been controllably synthesized by the trifluoromethanesulfonic acid-catalyzed nitrile trimerization reactions at room temperature via selecting different monomers. Platinum nanoparticles are well dispersed in CTF-T1, which is ascribed to the synergistic effects of the coordination of triazine moieties and the nanoscale confinement effect of CTFs. CTF-T1 exhibits excellent photocatalytic activity and stability for H2 evolution in the presence of platinum under visible light irradiation ( λ ≥ 420 nm). The activity and stability of CTF-T1 are comparable to those of g-C3N4. Importantly, as a result of the tailorable electronic and spatial structures of CTFs that can be achieved through the judicial selection of monomers, CTFs not only show great potential as organic semiconductor for photocatalysis but also may provide a molecular-level understanding of the inherent heterogeneous photocatalysis. [ABSTRACT FROM AUTHOR]

Frontispiece: A covalent triazine‐based framework (CTF) possessing a graphene‐like layered morphology demonstrates excellent photocatalytic activity and stability in splitting water under visible light irradiation. Due to the tailorable electronic and spatial structures of CTFs, they not only show great potential as organic semiconductors for photocatalysis but also provide a molecular‐level understanding of the inherent heterogeneous photocatalysis. Further details can be found in the article by J. Bi,* W. Fang, L. Li, J. Wang, S. Liang, Y. He, M. Liu, and L. Wu* on page 1799. [ABSTRACT FROM AUTHOR]

[Display omitted] Covalent organic frameworks (COFs) are crystalline porous materials with enormous potential for realizing solar-driven CO 2 -to-fuel conversion, yet the sluggish transfer/separation of photoinduced electrons and holes remains a compelling challenge. Herein, a step (S)-scheme heterojunction photocatalyst (CuWO 4 -COF) was rationally fabricated by a thermal annealing method for boosting CO 2 conversion to CO. The optimal CuWO 4 /COF composite sample, integrating 10 wt% CuWO 4 with an olefin (C═C) linked COF (TTCOF), achieved a remarkable gas–solid phase CO yield as high as 7.17 ± 0.35 μmol g−1h−1 under visible light irradiation, which was significantly higher than the pure COF (1.6 ± 0.29 μmol g−1h−1). The enhanced CO 2 conversion rate could be attributable to the interface engineering effect and the formation of internal electric field (IEF) directing from TTCOF to CuWO 4 according to the theoretical calculation and experimental results, which also proves the electrons transfer from TTCOF to CuWO 4 upon hybridization. In addition, driven by the IEF, the photoinduced electrons can be steered from CuWO 4 to TTCOF under visible light irradiation as well-elucidated by in-situ irradiated X-ray photoelectron spectroscopy, verifying the S-scheme charge transfer pathway over CuWO 4 /COF composite heterojunctions, which greatly foster the photoreduction activity of CO 2. The preparation technique of the S-scheme heterojunction photocatalyst in this study provides a paradigmatic protocol for photocatalytic solar fuel generation. [ABSTRACT FROM AUTHOR]

Designing photocatalysts with well-defined structure-function relationships is imperative for propelling the progression of desired photocatalytic oxidation. Herein, the efficient conversion of solar energy to H 2 O 2 and subsequently to hydroxyl radicals (•OH) is achieved through a synergistic interplay between olefin linkage (-C C-) and spatially separated benzene-triazine dual reaction sites within covalent organic frameworks (COFs). The upgraded -C C- can increase the conjugation degree of COFs, which establishes an expanded superstructure for boosting charge separation/transfer and stability. This precise modulation renders more opportunities for the hot electrons to migrate to the benzene site for solar-to-H 2 O 2 generation, and to the triazine site for H 2 O 2 -to-•OH, separately. The optimized •OH generation pathway enables remarkable oxidation performances against recalcitrant organic pollutants, and pathogenic microorganisms under visible light irradiation. This work provides new insights for tuning the synergistic interactions of various building blocks within the COFs for the selective generation of highly reactive •OH for environmental remediation. [Display omitted] • COFs with decisive structure-function relationship was tailored for •OH production. • ‐C C- bridge enhances conjugation and thereof the e- transfer and stability. • Site-specific functions: benzene drives O 2 to H 2 O 2 , triazine activates H 2 O 2 to •OH. • The oxidation power was proceeded through CB-e- rather than VB-h+. [ABSTRACT FROM AUTHOR]

Graphical abstract The Lewis acid sites (Ti) in TNS would selectively adsorb OH in cinnamyl alcohol forming surface C O···Ti O coordination species. Under visible light irradiation, interface charge transfer occurs from C O to Ti O , resulting in the activation of cinnamyl alcohol and the charge enrichment in Ti atoms of TiO 6. The molecule O 2 would be adsorbed on the electron enriched Ti atoms and reduced to O 2 − for the oxidation of alcohol. Due to the hybrid electronic states of Cu-Cu 2 O, the interface electronic transfer kinetics are tuned to inhibit the intramolecular hydrogen transfer for dominating the selectivity towards cinnamaldehyde. The synergistic effect of surface coordination-activation-photocatalysis enables an efficient and green synthesis. Highlights • The coordination of hydroxyl in alcohol with surface Lewis acid sites of H 1.4 Ti 1.65 O 4 ·H 2 O nanosheets. • Directional interface charges transfer from alcohol to nanosheet occur via surface coordination species. • The hybrid electronic states of Cu-Cu 2 O tune interface charges transfer kinetics. • Synergistic surface coordination-activation-photocatalysis for precies synthesis. Abstract A multifunctional photocatalyst is constructed based on Cu-Cu 2 O hybrid and monolayer H 1.4 Ti 1.65 O 4 ·H 2 O nanosheets via an in situ photo-deposition process (Cu-Cu 2 O/TNS). The prepared sample enables the oxidation of cinnamyl alcohol to cinnamaldehyde with over 95% of selectivity under visible light irradiation using molecule O 2 as the oxidant. In situ FTIR spectra suggest that the Lewis acid sites in TNS would selectively adsorbed the hydroxyl of cinnamyl alcohol forming surface C O∙∙∙Ti O coordination species. UV-DRS spectra reveal that light adsorption of TNS can be extended to visible light region due to the interface charges transfer from C OH to Ti O via the surface coordination, resulting in the activation of OH in alcohol. In situ ESR further indicates that directional interface charge transfer induces the charge enrichment in Ti atoms of TiO 6 , facilitating O 2 adsorption. XAFS results reveal that the hybrid electronic states of Cu-Cu 2 O efficiently improve the interface electronic transfer kinetics to inhibit the intramolecular hydrogen transfer for dominating the selectivity towards cinnamaldehyde. This work highlights the synergistic effect of surface coordination-activation-photocatalysis for selective photosynthesis of fine chemicals. [ABSTRACT FROM AUTHOR]

Monolayer H 1.4 Ti 1.65 O 4 ·H 2 O nanosheet (denoted as NST) has been prepared as a photocatalyst for the oxidation of furfuryl alcohol (denoted as FA) to furaldehyde under visible light irradiation. The photocatalytic activity of NST is over 10 times higher than that of its layered counterpart. This enhanced activity may be attributed to the high percentage of exposed Lewis acid sites in NST. The in-situ FTIR result suggests that FA are efficiently chemosorbed on the exposed Lewis acid sites forming the surface coordination species via C O groups, resulting in the activation of FA. The surface coordination species would respond to visible light absorption. Furthermore, The XAFS result shows that the signals for Ti O and Ti–Ti in NST are weaker dramatically and the signals positions are shifted by 0.03 Å in the higher R direction as compared with those in layered counterpart, suggesting the more exposed Ti and O defects in NST. The oxygen molecules absorbed on these surface defects are activated forming O 2 − by photo-electrons under visible light irradiation. Finally, a possible mechanism has been proposed at a molecular level. [ABSTRACT FROM AUTHOR]

CdS quantum dots (QDs) are excellent visible-light-driven photocatalysts due to their unique small size (<10 nm), suitable band energy structure, and short charge transportation length. Unfortunately, the easy aggregation of CdS QDs to form larger particles results in a higher recombination rate for photoinduced electron-hole pairs, which deteriorates the photocatalytic activity. Here, we report in situ growth of CdS QDs with high dispersion and stability on covalent triazine-based frameworks (CTFs) via a facile photoreduction method. The photocatalytic H 2 evolution activity of CdS QD-loaded CTFs is effectively enhanced to approximately 55 and 4 times than that of pristine CTFs and bulk CdS, respectively. This enhanced photocatalytic performance is mainly ascribed to the higher separation rate of photogenerated carriers resulting from synergistic QD-on-sheet interactions between CdS QDs and CTFs. This work develops an efficient one-pot strategy to prepare metal-sulfide QDs with high dispersion and underlines the potential of utilizing CTFs as a suitable platform to develop efficient photocatalytic systems. • ● The growth of CdS QDs on CTF-1 was achieved by a facile in situ photoreduction method. • The CdS QD-loaded CTF-1 showed higher H 2 evolution activity over pristine CTF-1 and bulk CdS. • The enhanced photocatalytic activity was mainly ascribed to the higher separation of the carriers. • The higher separation was due to the synergistic QD-on-sheet interactions between CdS QDs and CTF-1. [ABSTRACT FROM AUTHOR]