Covalent organic frameworks (COFs) were prepared through imine condensation reaction of hydrazine hydrate with hydroxy-1,3,5-triformylbenzenes, containing a varying number of hydroxyl groups, affording the microporous materials called . The role of intramolecular hydrogen bonding formation (conformational locking effects) in the crystallinity of the resulting COFs was evaluated. The results indicate that the increase of the number of conformational locks increases the symmetry of moieties during nucleation and crystal growth, resulting in less defects in the product structure. The use of aniline as modulator, with in situ formation of an intermediate imine, was also evaluated and proved to be beneficial in the case where the number of conformational locks is insufficient to afford high crystallinity. The use of the modulator for RIO-11 resulted in greater crystallinity and a 5.3-fold increase of its pristine BET surface area. Narrower monomodal pore size distributions, with cylindrical pores, were shown to be responsible for the greater surface area in these cases.

Sustainability in chemistry heavily relies on heterogeneous catalysis. Enzymes, the main catalyst for biochemical reactions in nature, are an elegant choice to catalyze reactions due to their high activity and selectivity, although they usually suffer from lack of robustness. To overcome this drawback, enzyme‐decorated nanoporous heterogeneous catalysts were developed. Three different approaches for Candida antarctica lipase B (CAL‐B) immobilization on a covalent organic framework (PPF‐2) were employed: physical adsorption on the surface, covalent attachment of the enzyme in functional groups on the surface and covalent attachment into a linker added post‐synthesis. The influence of the immobilization strategy on the enzyme uptake, specific activity, thermal stability, and the possibility of its use through multiple cycles was explored. High specific activities were observed for PPF‐2‐supported CAL‐B in the esterification of oleic acid with ethanol, ranging from 58 to 283 U mg−1, which was 2.6 to 12.7 times greater than the observed for the commercial Novozyme 435.

The development of efficient catalytic systems is a fundamental aspect for the straightforward production of chemicals. During the last years, covalent organic frameworks (COFs) emerged as an exciting class of organic nanoporous materials. Due to their pre‐designable structure, they can be prepared with distinct physicochemical characteristics, specific pore sizes, and tunable functional groups. Moreover, associated with their stability in different media, these materials are considered promising supports for enzyme immobilization. Herein, it is highlighted the recent literature of enzyme immobilization in COFs, the main immobilization strategies, and the catalytic applications of these composites.

Covalent organic frameworks (COFs) were investigated towards their CO 2 capture properties by thermogravimetric analysis at 1 atm and 40°C. These microporous COFs bear in common the azine backbone composed of hydroxy-benzene moieties but differ in the relative number of hydroxyl groups present in each material. Thus, their sorption capacities were studied as a function of their textural and chemical properties. Their maximum CO 2 uptake values showed a strong correlation with an increasing specific surface area, but that property alone could not fully explain the CO 2 uptake data. Hence, the specific CO 2 uptake, combined with DFT calculations, indicated that the relative number of hydroxyl groups in the COF backbone acts as an adsorption threshold, as the hydroxyl groups were indeed identified as relevant adsorption sites in all the studied COFs. Additionally, the best performing COF was thoroughly investigated, experimentally and theoretically, for its CO 2 capture properties in a variety of CO 2 concentrations and temperatures, and showed excellent isothermal recyclability up to 3 cycles.

Among various porous solids for gas separation and purification, metal-organic frameworks (MOFs) are promising materials that potentially combine high CO 2 uptake and CO 2 /N 2 selectivity. So far, within the hundreds of thousands of MOF structures known today, it remains a challenge to computationally identify the best suited species. First principle-based simulations of CO 2 adsorption in MOFs would provide the necessary accuracy; however, they are impractical due to the high computational cost. Classical force field-based simulations would be computationally feasible; however, they do not provide sufficient accuracy. Thus, the entropy contribution that requires both accurate force fields and sufficiently long computing time for sampling is difficult to obtain in simulations. Here, we report quantum-informed machine-learning force fields (QMLFFs) for atomistic simulations of CO 2 in MOFs. We demonstrate that the method has a much higher computational efficiency (∼1000×) than the first-principle one while maintaining the quantum-level accuracy. As a proof of concept, we show that the QMLFF-based molecular dynamics simulations of CO 2 in Mg-MOF-74 can predict the binding free energy landscape and the diffusion coefficient close to experimental values. The combination of machine learning and atomistic simulation helps achieve more accurate and efficient in silico evaluations of the chemisorption and diffusion of gas molecules in MOFs.

A thermally stable carbocationic covalent organic network (CON), named RIO‐70 was prepared from pararosaniline hydrochloride, an inexpensive dye, and triformylphloroglucinol in solvothermal conditions. This nanoporous organic material has shown a specific surface area of 990 m2 g−1 and pore size of 10.3 Å. The material has CO2 uptake of 2.14 mmol g−1 (0.5 bar), 2.7 mmol g−1 (1 bar), and 6.8 mmol g−1 (20 bar), the latter corresponding to 3 CO2 molecules adsorbed per pore per sheet. It is shown to be a semiconductor, with electrical conductivity (σ) of 3.17×10−7 S cm−1, which increases to 5.26×10−4 S cm−1 upon exposure to I2 vapor. DFT calculations using periodic conditions support the findings.

This contribution presents four dye-based CONs derived from the reaction of triformylphloroglucinol with thionin acetate (RIO-43), safranin chloride (RIO-51), phenosafranin (RIO-47), and Bismarck brown Y (RIO-55). These materials, called Covalent Organic Networks (CONs), are insoluble solids formed by organic lamellar stacked structures and present permanent porosity, light absorption across the whole visible spectrum, fluorescence, ion exchange capability, and ion and electron conductivity. Periodic DFT calculations carried out indicated that the bent nature of most of those building blocks affords conductive extended materials containing pores with the shape of three-petal flowers, with the anion positioned at the petals. The turbostratic disorder makes only the center of the flower-shaped pores accessible, decreasing the specific surface areas. The material that has a higher surface area is the one derived from thionin acetate (RIO-43), such as the highest electrical conductivity (1.96 × 10 -5 S cm −1 ), followed by RIO-47 (1.12 × 10 -7 S cm −1 ), RIO-55 (1.58 × 10 -7 S cm −1 ) and RIO-51 (3.26 × 10 -7 S cm −1 ).

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