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Two comparable models of BiOI/BiOCl heterojuctions with different interface structures (crystal surface orientation and crystal surface combination), denoted as BiOI(001)/BiOCl(001) and BiOI(001)/BiOCl(010), have been prepared via integrating heterojuncton nanostructure construction with crystal facet engineering. BiOI(001)/BiOCl(010) had a greater degree of lattice mismatch and displayed higher visible-light photocatalytic activity than BiOI(001)/BiOCl(001). In general, the activity of a photocatalyst (ηPC) has a positive correlation with light harvesting (ηLH), charge separation (ηCS), and charge injection (ηCI). On the basis of the experimental results, we considered that the higher ηCI value of BiOI(001)/BiOCl(010) was the main reason for its better visible-light photocatalytic performance. In combination with theoretical calculations, we found that the higher ηCI value of BiOI(001)/BiOCl(010) was the result of a shorter photogenerated electron diffusion distance, assisted by the self-induced internal electric fields of the BiOCl slabs. This indicated that the crystal facet combination is the key to enhancing the photocatalytic activity of BiOI/BiOCl. Our work offers an archetype for the further design of heterojunction photocatalysts with a fine tuning of the interface structures in order to reach optimized charge injection and enhanced photocatalytic activity.

Fabricating heterojunction photocatalysts is an important strategy for speeding up the separation rate of photogenerated charge carriers, which is attracting greater interest. However, the choice of three factors, individual materials, band offsets, and effective interfaces, is still important for fabricating efficient heterojunction photocatalysts. Herein, efficient g-C3N4/Zn2GeO4 photocatalysts with effective interfaces were designed by controlling the surface charges of the two individual materials inside the same aqueous dispersion medium, making use of the electrostatic attraction between oppositely charged particles. The g-C3N4/Zn2GeO4 heterojunction with opposite surface charge (OSC) showed higher visible-light photocatalytic activity for degradation of methylene blue than those of pure g-C3N4, pure Zn2GeO4, and the g-C3N4/Zn2GeO4 with identical surface charge (ISC). The investigation of the light absorption spectrum, adsorption ability, and photocurrent responses revealed that the improved separation of photogenerated carriers was the main reason for the enhancement of the OSC g-C3N4/Zn2GeO4 sample's photocatalytic activity. By combining with theoretical calculations, we investigated the microscopic mechanisms of interface interaction and charge transfer between g-C3N4 and Zn2GeO4. The photogenerated electrons in the g-C3N4 N 2p states directly excited into the Zn 4s and Ge 4s hybrid states of Zn2GeO4. The strategy of designing and preparing a g-C3N4/Zn2GeO4 composite catalyst in this work is very useful for fabricating other efficient heterojunction photocatalysts.

Understanding the thermal aggregation behavior of metal atoms is important for the synthesis of supported metal clusters. Here, derived from a metal–organic framework encapsulating a trinuclear FeIII2FeII complex (denoted as Fe3) within the channels, a well‐defined nitrogen‐doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacement of FeII by other metal(II) ions (e.g., ZnII/CoII) via synthesizing isostructural trinuclear‐complex precursors (Fe2Zn/Fe2Co), namely the “heteroatom modulator approach”, is inhibiting the aggregation of Fe atoms toward nanoclusters with formation of a stable iron dimer in an optimal metal–nitrogen moiety, clearly identified by direct transmission electron microscopy and X‐ray absorption fine structure analysis. The supported iron dimer, serving as cooperative metal–metal site, acts as efficient oxygen evolution catalyst. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities.

We present a systematic investigation of the microscopic mechanism of interface interaction, charge transfer and separation, as well as their influence on the photocatalytic activity of heterojunctions by a combination of theoretical calculations and experimental techniques for the g-C 3 N 4 -ZnWO 4 composite. HRTEM results and DFT calculations mutually validate each other to indicate the reasonable existence of g-C 3 N 4 (001)-ZnWO 4 (010) and g-C 3 N 4 (001)-ZnWO 4 (011) interfaces. The g-C 3 N 4 -ZnWO 4 heterojunctions show higher photocatalytic activity for degradation of MB than pure g-C 3 N 4 and ZnWO 4 under visible-light irradiation. Moreover, the heterojunctions significantly enhance the oxidation of phenol in contrast to pure g-C 3 N 4 , the phenol oxidation capacity of which is weak, clearly demonstrating a synergistic effect between g-C 3 N 4 and ZnWO 4 . Interestingly, based on the theoretical calculations, we find that electrons in the upper valence band can be directly excited from g-C 3 N 4 to the conduction band, that is, the W 5d orbital of ZnWO 4 , under visible-light irradiation, which should yield well-separated electron-hole pairs, with high photocatalytic performance in g-C 3 N 4 -ZnWO 4 heterojunctions as shown by our experiment. The microcosmic mechanisms of interface interaction and charge transfer in this system can be helpful for fabricating other effective heterostructured photocatalysts.

Highlights In this review, we survey the recent developments in the fabrication of metal–organic framework (MOF)-derived porous semiconductor photocatalysts toward four kinds of energy-/environment-related reactions.A comprehensive summary of highly efficient MOF-derived photocatalysts, particularly porous metal oxides and metal sulfides, and their heterostructures are provided.Enhanced photocatalytic performance achieved with MOF-derived porous heterostructures as the photocatalyst is discussed in detail.

ZnWO 4 /BiOI heterostructures with different constituents are synthesized via a chemical bath approach under mild conditions by tuning the Zn/Bi molar ratios. The obtained ZnWO 4 /BiOI heterostructures display high photocatalytic activities in degradation of MO and photocurrent response under visible light irradiation. Combining the experimental findings, first-principles calculations are used to investigate the surface geometry structures and the work functions of the ( 011) and ( 010) surfaces of the ZnWO 4 phase and the (001) surface of the BiOI phase. The results show that the lattice and energy levels between the ZnWO 4 and BiOI phases match well with each other to be capable of forming efficient ZnWO 4 /BiOI p-n heterojunction structures. This match promotes the separation and transfer of photoinduced electron-hole pairs at the interface, resulting in the excellent photocatalytic performance of the ZnWO 4 /BiOI heterostructures. Our findings show that the formation of a heterostructure would possess the excellent photocatalytic activities only if the lattice and energy level match between the two semiconductors was satisfied, which is of great importance for designing and developing more efficient heterostructured photocatalysts.

CuO as a catalyst has shown promising application prospects in photocatalytic splitting of water into hydrogen (H2). However, the instability of CuO in amine aqueous solution limits the applications of CuO‐based photocatalysts in the photocatalytic H2 evolution. In this work, a novel dodecahedral nitrogen (N)‐doped carbon (C) coated CuO‐In2O3 p–n heterojunction (DNCPH) is designed and synthesized by directly pyrolyzing benzimidazole‐modified dodecahedral Cu/In‐based metal‐organic frameworks, showing long‐term stability in triethanolamine (TEOA) aqueous solution and excellent photocatalytic H2 production efficiency. The improved stability of DNCPH in TEOA solution is ascribed to the alleviation of electron deficiency in CuO by forming the p–n heterojunction and the protection with coated N‐doped C layer. Based on detailed theoretical calculations and experimental studies, it is found that the improved separation efficiency of photogenerated electron/hole pairs and the mediated adsorption behavior (|∆GH*|→0) by coupling N‐doped C layer with CuO‐In2O3 p–n heterojunction lead to the excellent photocatalytic H2 production efficiency of DNCPH. This work provides a feasible strategy for effectively applying CuO‐based photocatalysts in photocatalytic H2 production.