Zi-Jian Zhou’s research while affiliated with East China University of Science and Technology and other places

The development of synthetic methods capable of converting elemental sulfur into conjugated porous sulfur‐rich polymers remains a great challenge, although direct utilization of this readily available feedstock can significantly enrich its uses and circumvent environmental problems during sulfur storage. We report herein mechanochemical (MC) nucleophilic aromatic substitution (SNAr) that enables sulfur conversion into thianthrene‐bridged porous ladder polymer networks with dense donor‐acceptor (D−A) molecular junctions. We demonstrate that the key lies in the generation of bent thianthrene units through a solid‐state ball‐milling condensation reaction between 1,2‐dihaloarenes and elemental sulfur. We also show that the assembling of D−A structural motifs into porous networks affords efficient visible‐light‐driven photocatalytic reduction of carbon dioxide (CO2) with water (H2O) vapor, in the absence of any additional photosensitizer, sacrificial agents or cocatalysts. Exceptional photoinduced charge separation along with boosted exciton dissociation results in a high‐performance of carbon monoxide (CO) production rate of 306.1 μmol g⁻¹ h⁻¹ with near 100 % CO selectivity, which is accompanied by H2O oxidation to O2, as confirmed by both experimental and theoretical results. We anticipate this novel MC SNAr approach will advance processing techniques for direct sulfur utilization and facilitate new possibilities for the synthesis of D−A ladder polymer networks with promising potential in photocatalysis.

The development of synthetic methods capable of converting elemental sulfur into conjugated porous sulfur‐rich polymers remains a great challenge, although direct utilization of this readily available feedstock can significantly enrich its uses and circumvent environmental problems during sulfur storage. We report herein mechanochemical (MC) nucleophilic aromatic substitution (SNAr) that enables sustainable sulfur conversion into thianthrene‐bridged porous ladder polymer networks with dense donor‐acceptor (D‐A) molecular junctions. We demonstrate that the key lies in the generation of bent thianthrene units through a solid‐state ball‐milling condensation reaction between 1,2‐dihaloarenes and elemental sulfur. The assembling of D‐A structural motifs into porous networks affords efficient visible‐light‐driven photocatalytic reduction of carbon dioxide (CO2) with water (H2O) vapor, in the absence of any additional photosensitizer, sacrificial agents or cocatalysts. Exceptional photoinduced charge separation along with boosted exciton dissociation results in a high‐performance of carbon monoxide (CO) production rate of 306.1 μmol g–1 h–1 with near 100% CO selectivity, which is accompanied by H2O oxidation to O2, as confirmed by both experimental and theoretical results. We anticipate this novel MC SNAr approach will advance processing techniques for sustainable sulfur utilization and facilitate new possibilities for the synthesis of D‐A ladder polymer networks with promising potential in photocatalysis.

The conversion of CO2 to C2 through photocatalysis poses significant challenges, and one of the biggest hurdles stems from the sluggishness of the multi‐electron transfer process. Herein, taking metal–organic framework (MOF, PFC‐98) as a model photocatalyst, we report a new strategy to facilitate charge separation. This strategy involves matching the energy levels of the lowest unoccupied node and linker orbitals of the MOF, thereby creating the lowest unoccupied crystal orbital (LUCO) delocalized over both the node and linker. This feature enables the direct excitation of electrons from photosensitive linker to the catalytic centers, achieving a direct charge transfer (DCT) pathway. For comparison, an isoreticular MOF (PFC‐6) based on analogue components but with far apart frontier energy level was synthesized. The delocalized LUCO caused the presence of an internal charge‐separated (ICS) state, prolonging the excited state lifetime and further inhibiting the electron‐hole recombination. The presence of ICS state prolongs the excited state lifetime and further inhibits the electron‐hole recombination. Moreover, it also induced abundant electrons accumulating at the catalytic sites, enabling the multi‐electron transfer process. As a result, the material featuring delocalized LUCO exhibits superior overall CO2 photocatalytic performance with high C2 production yield and selectivity.

The conversion of CO2 to C2 through photocatalysis poses significant challenges, and one of the biggest hurdles stems from the sluggishness of the multi‐electron transfer process. Herein, taking metal‐organic framework (PFC‐98) as a model photocatalyst, we report a new strategy to facilitate charge separation. This strategy involves matching the energy levels of the lowest unoccupied node and linker orbitals of the MOF, thereby creating the lowest unoccupied crystal orbital (LUCO) delocalized over both the node and linker. This feature enables the direct excitation of electrons from photosensitive linker to the catalytic centers, achieving a direct charge transfer (DCT) pathway. For comparison, an isoreticular MOF (PFC‐6) based on analogue components but with far apart frontier energy level was synthesized. The delocalized LUCO caused the presence of an internal charge‐separated state (ICS), prolonging the excited state lifetime and further inhibiting the electron‐hole recombination. The presence of an internal charge‐separated state (ICS) prolongs the excited state lifetime and further inhibits the electron‐hole recombination. Moreover, it also induced abundant electrons accumulating at the catalytic sites, enabling the multi‐electron transfer process. As a result, the material featuring delocalized LUCO exhibits superior overall CO2 photocatalytic performance with high C2 production yield and selectivity.

The establishment of active sites as the frustrated Lewis pair (FLP) has recently attracted much attention ranging from homogeneous to heterogeneous systems in the field of catalysis. Their unquenched reactivity of Lewis acid and base pairs in close proximity that are unable to form stable adducts has been shown to activate small molecules such as dihydrogen heterolytically. Herein, we show that grafted Ru metal-organic framework-based catalysts prepared via N-containing linkers are rather catalytically inactive for H2 activation despite the application of elevated temperatures. However, upon light illumination, charge polarization of the anchored Ru bipyridine complex can form a transient Lewis acid-base pair, Ru+-N- via metal-to-ligand charge transfer, as confirmed by time-dependent density functional theory (TDDFT) calculations to carry out effective H2-D2 exchange. FTIR and 2-D NMR endorse the formation of such reactive intermediate(s) upon light irradiation.