Anastasiya V. Bavykina

Challenges in the Greener Production of Formates/Formic Acid, Methanol, and DME by Heterogeneously Catalyzed CO2 Hydrogenation Processes

The recent advances in the development of heterogeneous catalysts and processes for the direct hydrogenation of CO2 to formate/formic acid, methanol, and dimethyl ether are thoroughly reviewed, with special emphasis on thermodynamics and catalyst design considerations. After introducing the main motivation for the development of such processes, we first summarize the most important aspects of CO2 capture and green routes to produce H2. Once the scene in terms of feedstocks is introduced, we carefully summarize the state of the art in the development of heterogeneous catalysts for these important hydrogenation reactions. Finally, in an attempt to give an order of magnitude regarding CO2 valorization, we critically assess economical aspects of the production of methanol and DME and outline future research and development directions.

Efficient production of hydrogen from formic acid using a Covalent Triazine Framework supported molecular catalyst

A heterogeneous molecular catalyst based on Ir(III) Cp* (Cp*=pentamethylcyclopentadienyl) attached to a covalent triazine framework (CTF) is reported. It catalyses the production of hydrogen from formic acid with initial turnover frequencies (TOFs) up to 27,000 h(-1) and turnover numbers (TONs) of more than one million in continuous operation. The CTF support, with a Brunauer-Emmett-Teller (BET) surface area of 1800 m(2)  g(-1), was constructed from an optimal 2:1 ratio of biphenyl and pyridine carbonitrile building blocks. Biphenyl building blocks induce mesoporosity and, therefore, facilitate diffusion of reactants and products whereas free pyridinic sites activate formic acid towards β-hydride elimination at the metal, rendering unprecedented rates in hydrogen production. The catalyst is air stable, produces CO-free hydrogen, and is fully recyclable. Hydrogen production rates of more than 60 mol L(-1)  h(-1) were obtained at high catalyst loadings of 16 wt % Ir, making it attractive towards process intensification.

Shaping Covalent Triazine Frameworks for the Hydrogenation of Carbon Dioxide to Formic Acid

A facile one‐step method to shape covalent triazine frameworks (CTFs) for catalytic applications is reported. Phase inversion of the CTF powder by using a polyimide as a binder in a microfluidic device results in the formation of composite spheres with accessible CTF porosity and a high mechanical and thermal stability. The fabricated spheres can be used to host organometallic complexes. The obtained shaped catalysts, Ir@CTF spheres, are active and fully recyclable in the direct hydrogenation of carbon dioxide into formic acid under mild reaction conditions (20 bar and 50–90 °C) and in the dehydrogenation of formic acid.

Sulfonated Porous Aromatic Frameworks as Solid Acid Catalysts

The synthesis, characterization, sulfonation, and catalytic performance of two new porous aromatic frameworks are presented. The polymers, which were obtained by the Suzuki–Miyaura cross‐coupling of the commercially available precursors 1,3,5‐tris(4‐bromophenyl)benzene or tris(4‐bromophenyl)amine and benzene‐1 4‐diboronic acid, only contain aromatic sp2 C−C and C−N bonds, display excellent thermal and chemical stability, and allow for post‐synthetic functionalization under very harsh reaction conditions. Upon post‐synthetic treatment at 160 °C in 98 wt % sulfuric acid, approximately 65 % of the benzene rings in the polymers were sulfonated. The materials were characterized by solid‐state NMR spectroscopy, X‐ray photoelectron spectroscopy, FTIR spectroscopy, and textural analysis. The sulfonated materials display an excellent catalytic performance in the acid‐catalyzed esterification of n‐butanol and acetic acid and have a similar or even superior performance to that of state‐of‐the‐art Amberlyst‐15 over multiple catalytic cycles.

Metal–Organic Framework Mediated Cobalt/Nitrogen‐Doped Carbon Hybrids as Efficient and Chemoselective Catalysts for the Hydrogenation of Nitroarenes

A Co@N‐doped carbon (Co@NC) hybrid was synthesized by thermal decomposition of the metal–organic framework (MOF) ZIF‐67 under N2 atmosphere. These hybrid materials exhibit outstanding catalytic activity and chemoselectivity for the conversion of a wide range of substituted nitroarenes to their corresponding anilines under relatively mild reaction conditions. The high catalytic performance is attributed to the formation of cobalt nanoparticles and to the presence of atomically dispersed Co species in close interaction with nitrogen‐doped graphene. Both active species are formed in situ during the pyrolytic transformation of ZIF‐67. The catalysts could be reused in consecutive runs, exhibiting a slightly lower activity ascribed to blockage of the active sites by strongly adsorbed reaction species. These results open up a pathway for the design of noble‐metal‐free solid catalysts for industrial applications.

Evidence for a chemical clock in oscillatory formation of UiO-66

Chemical clocks are often used as exciting classroom experiments, where an induction time is followed by rapidly changing colours that expose oscillating concentration patterns. This type of reaction belongs to a class of nonlinear chemical kinetics also linked to chaos, wave propagation and Turing patterns. Despite its vastness in occurrence and applicability, the clock reaction is only well understood for liquid-state processes. Here we report a chemical clock reaction, in which a solidifying entity, metal–organic framework UiO-66, displays oscillations in crystal dimension and number, as shown by X-ray scattering. In rationalizing this result, we introduce a computational approach, the metal–organic molecular orbital methodology, to pinpoint interaction between the tectonic building blocks that construct the metal–organic framework material. In this way, we show that hydrochloric acid plays the role of autocatalyst, bridging separate processes of condensation and crystallization.

Facile Method for the Preparation of Covalent Triazine Framework coated Monoliths as Catalyst Support: Applications in C1 Catalysis

A quasi chemical vapor deposition method for the manufacture of well-defined covalent triazine framework (CTF) coatings on cordierite monoliths is reported. The resulting supported porous organic polymer is an excellent support for the immobilization of two different homogeneous catalysts: (1) an IrIIICp*-based catalyst for the hydrogen production from formic acid and (2) a PtII-based catalyst for the direct activation of methane via Periana chemistry. The immobilized catalysts display a much higher activity in comparison with the unsupported CTF operated in slurry because of improved mass transport. Our results demonstrate that CTF-based catalysts can be further optimized by engineering at different length scales.

Base free transfer hydrogenation using a covalent triazine framework based catalyst

Isomerisation of allylic alcohols to saturated ketones can be efficiently catalysed by a heterogeneous molecular system resulting from IrIIICp* anchoring to a covalent triazine framework. The obtained catalysts are active, selective, and fully recyclable.

Revisiting Nitrogen Species in Covalent Triazine Frameworks

Covalent triazine frameworks (CTFs) are porous organic materials promising for applications in catalysis and separation due to their high stability, adjustable porosity, and intrinsic nitrogen functionalities. CTFs are prepared by ionothermal trimerization of aromatic nitriles; however, multiple side reactions also occur under synthesis conditions, and their influence on the material properties is still poorly described. Here we report the systematic characterization of nitrogen in CTFs using X-ray photoelectron spectroscopy. With the use of model compounds, we could distinguish several types of nitrogen species. By combining these data with textural properties, we unravel the influence that the reaction temperature, the catalyst, and the monomer structure and composition have on the properties of the resulting CTF materials.

Molecular-Scale Hybrid Membranes Derived from Metal-Organic Polyhedra for Gas Separation

The preparation and the performance of mixed matrix membranes based on metal-organic polyhedra (MOPs) are reported. MOP fillers can be dispersed as discrete molecular units (average 9 nm in diameter) when low filler cargos are used. In spite of the low doping amount (1.6 wt %), a large performance enhancement in permeability, aging resistance, and selectivity can be achieved. We rationalize this effect on the basis of the large surface to volume ratio of the filler, which leads to excellent dispersion at low concentrations and thus alters polymer packing. Although membranes based only on the polymer component age quickly with time, the performance of the resulting MOP-containing membranes meets the commercial target for postcombustion CO2 capture for more than 100 days.