Since their initial presentation in 2005 by Yaghi and co-workers, covalent organic frameworks (COFs) have been the focus of much development. Here we introduce mechanical bonds into COFs by employing a method that involves supramolecular self-assembly, dynamic imine-bond formation, and liquid-liquid interfacial condensation and produces a continuous 2D polyrotaxaneted film. A diamino-viologen linker is complexed with the macrocycle cucurbit[7]uril (CB[7]) to form pseudorotaxanes that then condense with an aromatic tri-aldehyde core at the interface of two solvents. The unrotaxanated COF is prepared by condensing the viologen and the trialdehyde in the absence of CB[7], and the chemical and physical properties of the formed films are compared. The CB[7]-encapsulated film is mechanically and thermally more robust and more luminescent. The synthetic strategy presented here allows the incorporation of mechanically interlocked molecules (MIMs) into polymeric materials and provides access to materials that have properties and functionalities that are yet to be explored.

The possibilities offered by molecular modeling tools to obtain relevant data at process conditions, while also gaining molecular insights on the techniques used for CO 2 capture and separation, are presented here using selected case studies. Two different technologies, absorption with amine-based systems and adsorption on porous materials, were explored, using the molecular-based equation of state, soft-Statistical Associating Fluid Theory (SAFT), and Grand Canonical Monte Carlo simulations, respectively. The aqueous monoethanolamine (MEA) system was set as the benchmark for absorption and compared to the performance of 8 alternative amine-based systems, while 16 adsorbents belonging to different families (zeolites, metal-organic frameworks, amorphous silicas, and activated carbons), bare or functionalized with alkylamines, were investigated for the separation of CO 2 by adsorption. In addition to obtaining molecular information on the CO 2 capture process, the models were further used to examine the CO 2 capture performance in terms of cyclic working capacity and energy index as key performance indicators, allowing the identification of promising systems that can improve the current ones to be further evaluated for separation in non-power industries. Results show that for the same total amine mass concentration, non-aqueous amine solvents have a 5-10% reduction in cyclic working capacity, and a 10-30% decrease in the energy index compared to their aqueous counterparts due to their lower heat of vaporization and specific heat capacity. In addition, M-MOF-74, NaX, and NaY structures present the best results for adsorption in temperature swing adsorption (TSA) processes. Similar values of energy requirements to those of amine-based systems (2-2.5 MJ kg CO 2 −1 ) were obtained for some of the adsorbent; however, the disadvantage of the TSA process versus absorption should be considered. These results confirm the reliability of molecular modeling as an attractive and valuable screening tool for CO 2 capture and separation processes.

Controlling the number of molecular switches and their relative positioning within porous materials is critical to their functionality and properties. The proximity of many molecular switches to one another can hinder or completely suppress their response. Herein, a synthetic strategy involving mixed linkers is used to control the distribution of spiropyran-functionalized linkers in a covalent organic framework (COF). The COF contains a spiropyran in each pore which exhibits excellent reversible photoswitching behavior to its merocyanine form in the solid state in response to UV/Vis light. The spiro-COF possesses an urchin-shaped morphology and exhibits a morphological transition to 2D nanosheets and vesicles in solution upon UV light irradiation. The merocyanine-equipped COFs are extremely stable and possess a more ordered structure with enhanced photoluminescence. This approach to modulating structural isomerization in the solid state is used to develop inkless printing media, while the photomediated polarity change is used for water harvesting applications.

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