More than 95% (in volume) of all today's chemical products are manufactured through catalytic processes, making research into more efficient catalytic materials a thrilling and very dynamic research field. In this regard, Metal Organic Frameworks (MOFs) offer great opportunities for the rational design of new catalytic solids, as highlighted by the unprecedented number of publications appearing over the last decade. In this review, the recent advances in the application of MOFs in heterogeneous catalysis are discussed. MOFs with intrinsic thermo-catalytic activity, as hosts for the incorporation of metal nanoparticles, as precursors for the manufacture of composite catalysts and those active in photo and electrocatalytic processes are critically reviewed. The review is wrapped up with our personal view on future research directions.

A Ni–Mo composite functions as a promising non-noble metal electrocatalyst for the hydrogen evolution reaction (HER) in alkaline water. Despite its industrial relevance, the kinetic origin of the high catalytic activity remains under debate. The present report discusses a reaction mechanism of HER on Ni–Mo catalysts by combining experimental and theoretical studies. In contrast to a Ni catalyst, a Ni–Mo catalyst is insensitive to CO gas introduced during HER. In situ spectroscopic measurements including Raman spectroscopy and electron paramagnetic resonance (EPR) show that Mo3+ prevails during HER catalysis. Density functional theory (DFT) simulations corroborate the thermodynamic stability and HER activity of Mo3+-containing centers on Ni(111) at HER potentials. Notably, Ni is demonstrated to play no direct role as a catalytic site but to effectively disperse and activate the oxidized catalytic Mo species. The results illustrate how to improve the electrocatalytic activity for alkaline HER.

Hydride transfers are key to a number of economically and environmentally important reactions, including H2 evolution and NADH regeneration. Therefore, the electrochemical generation of reactive hydrides has the potential to drive the electrification of chemical reactions to improve their sustainability for a green economy. Catalysts containing molybdenum (Mo) have recently been recognized as amongst the most promising non-precious catalysts for H2 evolution, but the mechanism of Mo in conferring this activity remains debated. In this work, we use a modified EPR setup to demonstrate the presence and catalytic role of a trapped Mo 3+ hydride in amorphous Mo sulfide (a-MoSx), one of the most active non-noble H2 evolution catalysts yet reported. We further confirm that this hydride is active for the selective electrochemical hydrogenation of the biologically important energy carrier NAD to its active NADH form and therefore utilized for biocatalysis, and that this reactivity applies to other HER-active forms of Mo sulfide. Our results represent the first direct experimental evidence of an immediate role for Mo in heterogeneous H2 evolution, placing a paramagnetic Mo center, as opposed to its partner atoms, 2 as an HER-active site with uniquely high activity for hydride formation and transfer. This mechanistic finding also reveals that Mo sulfides have potential as economic electrocatalysts for NADH regeneration in biocatalysis.

BackgroundThe MS4A gene family in humans includes CD20 (MS4A1), FcRβ (MS4A2), Htm4 (MS4A3), and at least 13 other syntenic genes encoding membrane proteins, most having characteristic tetraspanning topology. Expression of MS4A genes is variable in tissues throughout the body; however, several are limited to cells in the hematopoietic system where they have known roles in immune cell functions. Genes in the small TMEM176 group share significant sequence similarity with MS4A genes and there is evidence of immune function of at least one of the encoded proteins. In this study, we examined the evolutionary history of the MS4A/TMEM176 families as well as tissue expression of the phylogenetically earliest members, in order to investigate their possible origins in immune cells.Principal FindingsOrthologs of human MS4A genes were found only in mammals; however, MS4A gene homologs were found in most jawed vertebrates. TMEM176 genes were found only in mammals and bony fish. Several unusual MS4A genes having 2 or more tandem MS4A sequences were identified in the chicken (Gallus gallus) and early mammals (opossum, Monodelphis domestica and platypus, Ornithorhyncus anatinus). A large number of highly conserved MS4A and TMEM176 genes was found in zebrafish (Danio rerio). The most primitive organism identified to have MS4A genes was spiny dogfish (Squalus acanthus). Tissue expression of MS4A genes in S. acanthias and D. rerio showed no evidence of expression restricted to the hematopoietic system.Conclusions/SignificanceOur findings suggest that MS4A genes first appeared in cartilaginous fish with expression outside of the immune system, and have since diversified in many species into their modern forms with expression and function in both immune and nonimmune cells.

Semiconductor systems for photocatalytic overall water splitting into H 2 and O 2 gases typically require metal cocatalyst particles, such as Pt, to efficiently catalyze H 2 evolution. However, such metal catalyst surfaces also serve as recombination sites for H 2 and O 2 , forming H 2 O. We herein report the photon-induced fabrication of microporous SiO 2 membranes that can selectively restrict passage of O 2 and larger hydrated ions while allowing penetration of protons, water, and H 2 . The SiO 2 layers were selectively photodeposited on Pt nanoparticles on SrTiO 3 photocatalyst by using tetramethylammonium (TMA) as a structure-directing agent (SDA), resulting in the formation of core−shell Pt@SiO 2 cocatalysts. The resulting photocatalyst exhibited both improved overall water splitting performance under irradiation and with no H 2 /O 2 recombination in the dark. The function of the SiO 2 layers was investigated electrochemically by fabricating the SiO 2 layers on a Pt electrode via an analogous cathodic deposition protocol. The uniform, dense, yet amorphous layers possess microporosity originating from ring structures formed during the hydrolysis of the silicate precursor in the presence of TMA, suggesting a double-role for TMA in coordinating silicate to cathodic surfaces and in creating a microporous material. The resulting layers were able to function as a molecular sieve, allowing for exclusive H 2 generation while excluding unwanted side reactions by O 2 or ferricyanide. The SiO 2 layer is stable for extended periods of time in photocatalytic conditions, demonstrating promise as a nontoxic material for selective H 2 evolution.