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[Display omitted] • Hierarchical S-scheme TiO 2 @CoNi-MOF nanotubes were fabricated. • S-scheme heterojunction accelerates charge transfer and separation. • Hierarchical hybrid possesses more active sites and visible-light absorption. • Hierarchical hybrid exhibits enhanced activity and CH 4 selectivity. Efficient photocatalysts are of great importance for the photochemical conversion of CO 2 into fuels. Herein, S-scheme titanium dioxide@cobalt-nickel based metal–organic framework (TiO 2 @CoNi-MOF) heterojunction photocatalysts with high surface area and porosity are designed and fabricated by a multi-step controllable strategy. The photocatalytic activity of the composites can be optimized by adjusting the loading content of CoNi-MOF in TiO 2 @CoNi-MOF and molar ratios of Co2+ and Ni2+ in CoNi-MOF. The optimized hybrid photocatalyst showed a much higher CO 2 photoreduction activity than the control single-component samples (TiO 2 and CoNi-MOF) with a high CH 4 yield (41.65 μmol g−1 h−1) and selectivity (93.2%). The accelerated charge carrier separation induced by the S-scheme heterojunction significantly promoted the photocatalytic performance of TiO 2 @CoNi-MOF NTs. Meanwhile, the introduction of bimetallic CoNi-MOF nanosheets significantly resulted in the increase of active sites, CO 2 adsorbability, visible-light utilization, and CH 4 selectivity. Moreover, the S-scheme photoinduced charge transfer model of the TiO 2 @CoNi-MOF NTs photocatalyst was confirmed by photoluminescence spectroscopy, free radical trapping tests, and work function calculated from Kelvin probe. The work aims to design and fabricate heterojunction photocatalysts with high efficiency for solar fuel production. [ABSTRACT FROM AUTHOR]

[Display omitted] • Hierarchical S-scheme TiO 2 @CoNi-MOF nanotubes were fabricated. • S-scheme heterojunction accelerates charge transfer and separation. • Hierarchical hybrid possesses more active sites and visible-light absorption. • Hierarchical hybrid exhibits enhanced activity and CH 4 selectivity. Efficient photocatalysts are of great importance for the photochemical conversion of CO 2 into fuels. Herein, S-scheme titanium dioxide@cobalt-nickel based metal–organic framework (TiO 2 @CoNi-MOF) heterojunction photocatalysts with high surface area and porosity are designed and fabricated by a multi-step controllable strategy. The photocatalytic activity of the composites can be optimized by adjusting the loading content of CoNi-MOF in TiO 2 @CoNi-MOF and molar ratios of Co2+ and Ni2+ in CoNi-MOF. The optimized hybrid photocatalyst showed a much higher CO 2 photoreduction activity than the control single-component samples (TiO 2 and CoNi-MOF) with a high CH 4 yield (41.65 μmol g−1 h−1) and selectivity (93.2%). The accelerated charge carrier separation induced by the S-scheme heterojunction significantly promoted the photocatalytic performance of TiO 2 @CoNi-MOF NTs. Meanwhile, the introduction of bimetallic CoNi-MOF nanosheets significantly resulted in the increase of active sites, CO 2 adsorbability, visible-light utilization, and CH 4 selectivity. Moreover, the S-scheme photoinduced charge transfer model of the TiO 2 @CoNi-MOF NTs photocatalyst was confirmed by photoluminescence spectroscopy, free radical trapping tests, and work function calculated from Kelvin probe. The work aims to design and fabricate heterojunction photocatalysts with high efficiency for solar fuel production. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZnSe sensitized MIL-125(Ti)@TiO 2 hollow nanodisks are fabricated. • Multi-channel charge transfer routes benefit the charge and separation. • Hollow sandwich-like nanodisks exhibit a enhanced light utilization. • Synergy of compositions and structure results in an enhanced CO 2 reduction activity. Metal-organic frameworks-based hybrids with desirable components, structures, and properties have been proven to be promising functional materials for photocatalysis and energy conversion applications. Herein, we proposed and prepared ZnSe sensitized hierarchical TiO 2 nanosheets encapsulated MIL-125(Ti) hollow nanodisks with sandwich-like structure (MIL-125(Ti)@TiO 2 \ZnSe HNDs) through a successive solvothermal and selenylation reaction route using the as-prepared MIL-125(Ti) nanodisks as precursor. In the ternary MIL-125(Ti)@TiO 2 \ZnSe HNDs hybrid, TiO 2 nanosheets were transformed from MIL-125(Ti) and in situ grown on both sides of the MIL-125(Ti) shell, forming sandwich-like hollow nanodisks, and the ratio of MIL-125(Ti)/TiO 2 can be tuned by changing the solvothermal time. The ternary hybrids possess the advantages of enhanced incident light utilization and abundant accessible active sites originating from bimodal pore-size distribution and hollow sandwich-like heterostructure, which can effectively promote CO 2 photoreduction reaction. Especially, the formed multi-channel charge transfer routes in the ternary heterojunctions contribute to the charge transfer/separation and extend the lifespan of charge-separated state, thus boosting CO 2 photoreduction performance. The CO (513.1 μmol g−1h−1) and CH 4 (45.1 μmol g−1h−1) evolution rates over the optimized ternary hybrid were greatly enhanced compared with the single-component and binary hybrid photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] Photocatalytic CO 2 reduction into valuable fuel and chemical production has been regarded as a prospective strategy for tackling with the issues of the increasing of greenhouse gases and shortage of sustainable energy. A composite photocatalysis system employing a semiconductor enriched with oxygen vacancy and coupled with metallic cocatalyst can facilitate charge separation and transfer electrons. In this work, mesoporous TiO 2 and titanium-based perovskite oxides (BaTiO 3 and SrTiO 3) nanoparticle assembly incorporated with abundant oxygen vacancy and copper particles have been successfully synthesized for CO 2 photoreduction. As an example, the TiO 2 decorated with different amounts of Cu particles has an impact on photocatalytic CO 2 reduction into CH 4 and CO. Particularly, the optimal TiO 2 /Cu-0.1 exhibits nearly 13.5 times higher CH 4 yield (22.27 μmol g−1 h−1) than that of pristine TiO 2 (1.65 μmol g−1 h−1). The as-obtained BaTiO 3 /Cu-0.1 and SrTiO 3 /Cu-0.1 also show enhanced CH 4 yields towards photocatalytic CO 2 reduction compared with pristine ones. Based on the temperature programmed desorption (TPD) and photo/electrochemical measurements, the co-embedding of Cu particles and abundant oxygen vacancy into the titanium-based oxides could promote CO 2 adsorption capacity as well as separation and transfer of photoinduced electron-hole pairs, and finally result in efficient CO 2 photoreduction upon the TiO 2 /Cu, SrTiO 3 /Cu, and BaTiO 3 /Cu composites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ni and I substitutionally codoped TiO 2 phase junction was synthesized. • The photocalcatalysis for CO 2 reduction in water vapor was accomplished. • The selectivity of CH 4 product reached above 98%. • The electron transfer was enhanced by Ni(III)/Ni(II) pair. • The CO 2 adsorption mode was changed by the doping Ni/I. Ni and I co-doped TiO 2 nanoparticles with mixed anatase-brookite phase (Ni/I-TiO 2) were synthesized by the hydrothermal-calcination method for photocatalytic CO 2 reduction with H 2 O vapor. The I and Ni co-doping, anatase-brookite phase junction, as well as the presence of Ti(III) and Ni(III) endowed the catalyst with promoted visible light absorption, increased reduction ability of photogenerated electrons, facilitated charge separation and migration along with modulated CO 2 adsorption mode and capacity, ultimately resulting in boosted photocatalytic activity and product selectivity as compared with those of pure TiO 2. The CO, CH 4 and O 2 yields of the optimized Ni/I-TiO 2 reached 3.49, 158.25 and 246.30 μmol/g cat after 15 h of light illumination, which decreased slightly after 9 cycles, and the product selectivity was above 98 % for photocatalytic reduction of CO 2 to CH 4 with Ni and I co-doping. The in-situ FTIR results with the observation of CH 3 O and CH 3 intermediates confirmed CH 4 formation, and the possible mechanism of photocatalytic CO 2 reduction over Ni/I-TiO 2 was elucidated. This work provides new insights to pursue efficient catalysts for the selective photocatalytic CO 2 reduction to CH 4. [ABSTRACT FROM AUTHOR]