ABSTRACT
Beyond traditional paper, multifunctional nanopaper has received much attention in recent years. Currently, many nanomaterials have been successfully used as building units of nanopaper. However, it remains a great challenge to prepare flexible and freestanding metal-organic framework (MOF) nanopaper owing to the low aspect ratio and brittleness of MOF nanocrystals. Herein, this work develops a flexible and free-standing MOF nanopaper with MOF nanowires as building units. The manganese-based MOF (Mn-MOF) nanowires with lengths up to 100 µm are synthesized by a facile solvothermal method. Through a paper-making technique, the Mn-MOF nanowires interweave with each other to form a three-dimensional architecture, thus creating a flexible and free-standing Mn-MOF nanowire paper. Furthermore, the surface properties can be engineered to obtain high hydrophobicity by modifying polydimethylsiloxane (PDMS) on the surfaces of the Mn-MOF nanowire paper. The water contact angle reaches 130°. As a proof of concept, this work presents two potential applications of the Mn-MOF/PDMS nanowire paper: (i) The as-prepared Mn-MOF/PDMS nanowire paper is compatible with a commercial printer. The as-printed colorful patterns are of high quality, and (ii) benefiting from the highly hydrophobic surfaces, the Mn-MOF/PDMS nanowire paper is able to efficiently separate oil from water.
ABSTRACT
Exploitation of atomic-level principles to optimize the charge transfer on ultrathin 2D heterostructures is an emerging frontier in relieving the energy and environmental crisis. Herein, a facile "topological-atom-extraction" protocol is disclosed, i.e., selective extraction of Zn from ultrathin half-unit-cell ZnIn2 S4 (HZIS) can embed thin In2 O3 domain into 1.60 nm thick HZIS layer to create an atomically thin in-plane In2 O3 /HZIS heterostructure. Thanks to the optimal distance and capability of charge separation, the in-plane In2 O3 /HZIS heterostructure is among the best ZnIn2 S4 -based CO2 reduction reaction (CRR) photocatalysts, and indeed demonstrates a significant increase (from 6.8- to 128-fold) in CO production rate compared with those of out-plane ZIS@In2 O3 and out-plane In2 O3 -HZIScalcined heterostructures. Density Functional Theory simulation reveals that whereas the out-plane heterostructure has a much smaller ∆q of 0.2-0.25 e, the in-plane heterostructure with "zero distance contact" has an optimal ∆q of 1.05 e between In2 O3 and HZIS that induces remarkable charge redistribution on the in-plane heterojunction interface and creates local electric field confined within the ultrathin layer. The charge redistribution efficiently directs the charge-carrier separation in S-scheme photocatalytic system and endows long-lifetime carrier to CRR active HZIS. The findings demonstrate the strong versatility of engineering atomic-level heterojunctions for efficient catalysts design.
ABSTRACT
It is fascinating yet challenging to assemble anisotropic nanowires into ordered architectures of high complexity and intriguing functions. We exploited a facile strategy involving oriented etching of a metal-organic fragment (MOF) to advance the rational design of highly ordered nanostructures. As a proof of concept, a microscale MIL-68(In) single crystal was etched with a K3[Co(CN)6] solution to give a microtube composed of aligned MIL-68(In) nanorods. Annealing such a MIL-68(In) microtube readily created an unprecedented branched In2O3 mesocrystal by assembly of In2O3 nanorods aligned in order. The derived ordered-In2O3-ZnIn2S4 is more efficient in catalyzing visible-light-driven H2 evolution (8753 µmol h-1 g-1) outperforming the disordered-In2O3-ZnIn2S4 counterpart (2700 µmol h-1 g-1) as well as many other state-of-the-art ZnIn2S4-based photocatalysts. The ordered architecture significantly boosts the short-range electron transfer in an In2O3-ZnIn2S4 heterojunction but has a negligible impact on the long-range electron transfer among In2O3 mesocrystals. The density functional theory (DFT) calculation reveals that the oriented etching is achieved by the selective binding of the [Co(CN)6]3- etchant on the (110) plane of MIL-68(In), which can drag the In atoms out of the framework in order. Our findings could broaden the technical sense toward advanced photocatalyst design and impose scientific impacts on unveiling how ordered photosystems operate.
ABSTRACT
Fabrication of low-dimensional nano-MOFs as well as nanoparticles/metal-organic frameworks (MOFs) hybrids has sparked new scientific interests but remains a challenging task. Taking Cu3 (BTC)2 as a proof of concept, it is demonstrated thats NH3 â H2 O solution of a confined pH value can readily shape the bulk Cu3 (BTC)2 into nanoscale Cu3 (BTC)2 , beyond the need to control the crystal growth kinetics of MOFs. Adjusting the pH of NH3 â H2 O within a much small range (10-11) allows fine tuning over the size and shape of nanoscale Cu3 (BTC)2 . Particularly at pH = 11, NH3 â H2 O exhibits weak reducibility that triggers a reduction of part of Cu3 (BTC)2 into Cu2 O, while shaping the other into Cu3 (BTC)2 nanowires. Benefiting from the coincidence of reduction and etching effects, the newly generated Cu2 O dots can in situ anchor onto adjacent Cu3 (BTC)2 nanowires at highly dispersive state, forming a well-defined sponge-like architecture built of Cu2 O dots and nano-Cu3 (BTC)2 . The CuOx derived from annealing of the Cu2 O dots/nano-Cu3 (BTC)2 hybrid preserves the sophisticated sponge architecture and high porosity, and exhibits promising applications in phenol scavenging, with efficiency outperforming its counterparts and many other Cu-based catalysts reported in literature. It is anticipated that the findings here pave the way for the rational design of intricate nano-MOFs in a more efficient way.
