Molybdenum Sulfide within a Metal–Organic Framework for Photocatalytic Hydrogen Evolution from Water

Abstract

A representative metal–organic framework, NU-1000, was functionalized with MoSx. The previously determined crystal structure of the material, named MoSx-SIM, consists of monometallic Mo(IV) ions with two sulfhydryl ligands. The metal ions are anchored to the framework by displacing protons presented by the –OH/–OH2 groups on the Zr6 node. As shown previously, the MOF-supported complexes are electrocatalytic for hydrogen evolution from acidified water. The earlier electrocatalysis results, together with the nearly ideal formal potential of the Mo(IV/II) couple (i.e., nearly coincident with that of the hydrogen couple), and the physical proximity of UV-absorbing MOF linkers to the complexes, suggested to us that the linkers might behave photosensitizers for catalyst reduction, and subsequently, for H2 evolution from water. To our surprise, MoSx-SIM, when UV-illuminated in an aqueous buffer at near-neutral pH, displays a biphasic photocatalytic response: an initially slow rate of reaction, i.e. 0.56 mmol g−1 h−1, followed by an increase to 4 mmol g−1 h−1. Ex-situ catalyst examination revealed that nanoparticulate MoSx suspended within the reaction mixture is the actual catalyst. Thus, photo-assisted restructuring and detachment of the catalyst or pre-catalyst from the MOF node appears to be necessary for the catalyst to reduce water at neutral pH.

Single‐Site, Single‐Metal‐Atom, Heterogeneous Electrocatalyst: Metal–Organic‐Framework Supported Molybdenum Sulfide for Redox Mediator‐Assisted Hydrogen Evolution Reaction

“…After bulk electrolysis, 200 μL of the working electrode chamber headspace gas was injected into the GC. For details on the GC set‐up, see the reference . All sulfide‐based electrodes were prepared in an argon‐filled glovebox and the dried ethanol used for the suspension was purged with N 2 for 20 minutes prior to the addition to prevent excessive oxidation.…”

“…In this context, photo‐, electro‐, or photoelectrochemical reduction of water (or hydronium ions) to molecular hydrogen, i. e ., the hydrogen evolution reaction (HER), is ideal. Coupling HER to the corresponding oxidative reaction, namely molecular oxygen evolution, yields overall water splitting, and thus, molecular hydrogen formation in a carbon‐neutral manner.…”

MOF-enabled confinement and related effects for chemical catalyst presentation and utilization

“…In view of the role of mononuclear, binuclear and/or cluster-based metal-sulfur species as electron carriers and as cofactors for enzyme-catalysed reduction of protons to molecular hydrogen, and N 2 reduction to ammonia, replacing or converting the above metal-oxy species with or to metal-sulfur (sulfide, disulfide, thiolate, sulfhydryl) species could render many of these species functional for MOFintegrated reductive catalysis. 98,99,[319][320][321][322][323][324] Summarized in Fig. 57 are examples based on grafting single-metal-atom Mo(SH) 2 units to an open site on an eight-connected MOF.…”

“…The catalyst is competent for hydrogen evolution from aqueous acid when supplied with electrons either electrochemically 99,322 or photochemically. 321 Note that the coordination number and coordination geometry for these single-metal-atom sites differ from the nominally octahedral coordination environment of bulk molybdenum disulfide, a 2D layered material whose sulfur-rich edge sites (terminal sites) are known to be extraordinarily effective as electrocatalysts for hydrogen evolution reaction (HER). MoS 2 -SIM-NU-1000 (Fig.…”

Selective Mesitylene Oxidative Coupling Reaction by Metastructured Electrocatalyst Comprised of Carbonaceous Scaffold Coated with Pd Derived from Zeolitic Imidazole Framework

“…Different ZIFs can be selected as precursor material to provide Carbon scaffolds with contrasting diameters. Recently ZIF produced structured porous carbon has been used as a support and catalyst carrier [24][25][26] for selective dehydrogenation of alkanes [27], selective hydrogenation [28], selective epoxidation [29], selective hydrogenation of cinnamaldehyde [30], dye degradation [31] and other reactions [32][33][34][35][36][37], and for electrocatalytic oxygen [38]/hydrogen [39] evolution/reduction. However, the application of structured carbon framework originating from a ZIF is still unexplored for an electrocatalytic size-selective conversion.…”