Recent Progress of Metal Organic Frameworks-Based Electrocatalysts for Hydrogen Evolution,Oxygen Evolution,and Oxygen Reduction Reaction

Exploring efficient and cost-saving electrocatalysts is essential to the renewable energy storage and utilization,which is still in its embryonic period.MOFs have drawn tremendous attention due to their adjustability,abundant active sites,and plentiful pores.Notably,satisfactory electrocatalytic performance has been achieved by MOFs-based electrocatalysts comparable to traditional electrocatalysts.State-of-the-art works about the MOFs-based electrocatalysts for hydrogen evolution reaction(HER),oxygen evolution reaction(OER),and ORR were summarized in this review.This review comprises a series of modifying strategies of MOFs and their derivatives,from aspects of structure,composition,and morphology.Furthermore,the active sites and functional mechanisms’recognition are involved in this review expecting to provide reference for rationally designing efficient electrocatalysts.At last,the current status,challenges,and perspectives of MOFs-based electrocatalysts are also discussed.

Thermal expansion-quench of nickel metal-organic framework into nanosheets for efficient visible light CO_(2) reduction

Metal-organic framework nanosheets (MOF NNs) offer potential opportunities for many applications,but an efficient strategy for the scalable preparation of few-layered two-dimensional (2D) MOF NNs are still a major challenge.Herein,we present an efficient top-down method for the synthesis of the Ni-BDC(Ni_(2)(OH)_(2)(1,4-BDC);1,4-BDC=1,4-benzenedicarboxylate) nanosheets utilizing a novel thermal expansionquench method of the flowerlike bulky MOFs in liquid N2.The obtained Ni-BDC nanosheets exhibit significantly enhanced photocatalytic performance of reductive CO_(2)deoxygenation (7.0μmol h^(-1)mg^(-1)) under visible light illumination compared with the bulky MOFs,due to much higher surface area for CO_(2)adsorption,more abundant active sites exposed and stronger electron transport ability of the nanosheets.More importantly,this synthetic strategy can be extended to fabricate other MOF nanosheets which also exhibit significantly improved performance for deoxygenative CO_(2)reduction compared to their bulky counterparts.This work may provide a guideline for preparing other 2D layered photocatalysts materials to realize energy conversion applications.

Ultrafine PdRu Nanoparticles Immobilized in Metal-Organic Frameworks for Efficient Fluorophenol Hydrodefluorination under Mild Aqueous Conditions

Fluorinated organic compounds are of great importance to modern industries,while their release to the environment is inevitable,causing extreme environmental pollution and the subsequent hazardous effect on ecosystems.This is because the degradation of fluorinated compounds under mild conditions remains a challenging task due to the strong C-F bond strength.In this study,we report preparation of PdRu@MIL-101 through immobilizing ultrafine PdRu alloy nanoparticles with a mean diameter of∼2 nminto the metal-organic framework(MOF),MIL-101(Cr),which was highly active and stable in the hydrodefluorination of 4-fluorophenol(4-FP)under mild aqueous conditions.The optimized catalyst Pd0.5Ru0.5@MIL-101 achieved impressive hydrogenation performance with a 98.5% conversion of 4-FP and a 97.7% selectivity of cyclohexanol,much better than the single metal-doped Pd@MIL-101 and Ru@MIL-101 catalysts.The excellent catalytic behavior contributed to the synergistic effect of combining the PdRu alloying effect and the MOF nanospace confinement effect,providing a promising strategy to develop highly efficient hydrodefluorination catalysts to assist environmental restoration and green ecology.

Self-Assembly Ultrathin Fe-Terephthalic Acid as Synergistic Catalytic Platforms for Selective Hydrogenation

Alloy nanoparticles(NPs)with numerous exposed catalytic active sites have been extensively studied as efficient heterogeneous catalysts.However,it is challenging to synthesize alloy NP catalysts with high activity while avoiding aggregation.Herein,we report a facile method to encapsulate alloy NPs loaded metal–organic framework(MOF)catalysts(alloy NPs/MOFs)within an ultrathin metal–organic layer using a terephthalic acid(BDC)assisted method.A series of metal-BDC encapsulated PtM/MOFs(M=Fe,Co,and Ni)catalysts were synthesized successfully and showed significantly enhanced catalytic performance toward selective hydrogenation reaction.

Ir nanoclusters confined within hollow MIL-101(Fe)for selective hydrogenation ofα,β-unsaturated aldehyde

Although the selective hydrogenation ofα,β-unsaturated aldehyde to unsaturated alcohol(UOL)is an extremely important transformation,it is still a great challenge to achieve high selectivity to UOL due to thermodynamic favoring of the C=C hydrogenation over the C=O hydrogenation.Herein,we report that iridium nanoclusters(Ir NCs)confined within hollow MIL-101(Fe)expresses satisfied reaction activity(93.9%)and high selectivity(96.2%)for the hydrogenation of cinnamaldehyde(CAL)to cinnamyl alcohol(COL)under 1 bar H;atmosphere and room temperature.The unique hollow structure of MIL-101(Fe)benefits for the fast transport of reactant,ensuring the comparable reaction activity and better recyclability of Ir@MIL-101(Fe)than the counterparts which Ir NCs were on the surface of MIL-101(Fe).Furthermore,The X-ray photoelectron spectroscopy data indicates the electropositive Ir NCs,owing to the electron transfer from Ir to MIL-101(Fe),can interact with oxygen lone pairs,and Fourier transform infrared spectrum shows the Lewis acid sites in MIL-101(Fe)can strongly interact with C=O bond,which contributes to a high selectivity for COL.This work suggests the considerable potential of synergetic effect between hollow MOFs and metal nanoclusters for selective hydrogenation reactions.

Single-atomic Fe anchored on hierarchically porous carbon frame for efficient oxygen reduction performance

Exploring platinum group metal-free electrocatalysts with superior catalytic performance and favorable durability for oxygen reduction reaction is a remaining bottleneck in process of developing sustainable techniques in energy storage and conversion. Herein, a hierarchical porous single atomic Fe electrocatalyst(Fe/Z8-E-C) is rationally designed and synthesized via acid etching, calcination, adsorption of Fe precursor and recalcination processes. This unique electrocatalyst Fe/Z8-E-C shows excellent oxygen reduction performance with a half-wave potential of 0.89 V in 0.1 mol/L KOH, 30 m V superior to that of commercial Pt/C(0.86 V), which is also significantly higher than that of typical Fe-doped ZIF-8 derived carbon nanoparticles(Fe/Z8-C) with a half-wave potential of 0.84 V. Furthermore, Fe/Z8-E-C-based Zn-air battery exhibits greatly enhanced peak power density and specific capacity than those of original Fe/Z8-C,verifying the remarkable performance and practicability of this specially designed hierarchical structure due to its efficient utilization of the active sites and rapid mass transfer. This present work proposes a new method to rationally synthesize single atom electrocatalysts loaded on hierarchical porous frame materials for catalysis and energy conversion.