Braulio Rodríguez-Molina

Translating molecular-level dynamics of crystalline frameworks into macroscopic function remains a central challenge in the design of responsive materials. Here, we report that the intrinsic flexibility of COF-300 can be systematically characterized in the bulk powder and then harnessed in a processable composite film to achieve coupled optical and mechanical actuation. In powder form, COF-300 exhibits distinct responses to applied stimuli, including solvent vapors, acid-base environments, and temperature changes. Variable-temperature solid-state NMR reveals the thermally activated coalescence of the phenylene ring signals, and variable-temperature powder X-ray diffraction uncovers colossal anisotropic thermal expansion. Periodic TDA-DFT calculations trace the acid-induced chromism to both geometric distortion and protonation of framework. Embedding COF-300 into a poly(vinylidene fluoride) matrix produces a PVDF@COF film in which solvent vapors drive reversible bending–unbending motion synchronized with a visible color shift, and heating drives the same reversible motion. Exposure to HCl turns the film orange and locks both responses through imine protonation, while thermal deprotonation unlocks them, establishing a reversible chemical switch over framework dynamics. These findings show how molecular flexibility in a crystalline framework can translate into programmable macroscopic actuation, advancing the design of multifunctional solid-state actuators with integrated optical and mechanical output.

Cryogenic thermosalient motion arises from colossal anisotropic lattice expansion rather than solvent release, with rapid molecular rotation and macroscopic crystal motion occurring independently within the same material.

Pore functionalization of metal–organic frameworks (MOFs) remains a superb challenge for controlling intermolecular interactions and the resulting diffusion of guests. Herein, we report a modular presynthetic strategy to expand the chemical space of UiO-67 by incorporating structurally diverse dicarboxylate linkers synthesized via the Ugi four-component reaction (Ugi-4CR). This approach introduces amide-rich functionalities while preserving the fcu topology of the Zr-based framework, as confirmed by PXRD and solid-state 13C NMR spectroscopy. The Ugi-derived functionalization systematically modulates porosity and pore environment, which was further tuned through a multivariate (MTV) mixed-linker strategy. Nitrogen adsorption analysis reveals systematic modulation of surface area and pore accessibility with increasing functionalization. The prepared MOFs were used to adsorb catechol, a prototypical phenolic pollutant, which was quantified by HPLC. The MTV material exhibited the highest uptake, highlighting the interplay between pore accessibility and host–guest interactions, where excessive functionalization hinders adsorption. Overall, this work establishes multicomponent reactions as a versatile platform for tuning pore chemistry in MOFs while emphasizing the need to balance functionality to optimize performance.

Porous dynamic crystalline materials are highly valued for the connection between internal dynamics and functional performance, yet the controlled integration and interaction between multiple dynamic components within a single framework remain a fundamental challenge. Here, we employed the zirconium-based metal−organic framework UiO-68, constructed from a terphenyl dicarboxylate linker (Lrot), as a base scaffold to integrate a second dynamic component: a pyrrolo[3,2-b]pyrrole-derived linker with two azobenzene moieties (Lazo) into a family of Lrot:Lazo multivariate metal-organic frameworks (MTV-MOFs). After irradiation, solid-state UV-Vis and deuterium solid-state NMR revealed that both components exhibit independent dynamics within the framework. This work incorporates rotors and photoswitches into an MTV-MOF, and subsequent studies show that the uptake of hexafluorobenzene enables a Lazo photoisomeric-dependent effect on the rotational behavior of Lrot. The results allow us to expand the scope of responsive multidynamic crystalline materials toward the design of artificial molecular factories.

Harnessing mechanical motion in molecular crystals is a critical goal for developing novel energy conversion materials. Among known strategies, the ejection of guest molecules from the lattice via the jumping‐mate approach offers a direct means of propulsion. Here, we present isostructural cocrystals of indolo[3,2‐ a ]carbazole (ICZ) and ( E )‐1,2‐di(pyridin‐4‐yl)ethene (BPE) that incorporate solvents such as acetone, ethyl acetate, or tetrahydrofuran. X‐ray diffraction and solid‐state nuclear magnetic resonance (NMR) studies confirmed the presence of solvents or solvent mixtures. Upon heating, these channel‐type cocrystals exhibit a thermosalient effect, with temperature regulation achieved by releasing pure or solvent mixtures. Differential scanning calorimetry and thermogravimetry (DSC–TGA) analyses revealed that the transition temperatures changed progressively, demonstrating controllable thermal actuation through the release of occluded solvents. This work demonstrates a simple yet powerful way to regulate mechanical responses in molecular crystals, thereby advancing the design of responsive energy conversion materials.

Harnessing mechanical motion in molecular crystals is a critical goal for developing novel energy conversion materials. Among known strategies, the ejection of guest molecules from the lattice via the jumping‐mate approach offers a direct means of propulsion. Here, we present isostructural cocrystals of indolo[3,2‐ a ]carbazole (ICZ) and ( E )‐1,2‐di(pyridin‐4‐yl)ethene (BPE) that incorporate solvents such as acetone, ethyl acetate, or tetrahydrofuran. X‐ray diffraction and solid‐state nuclear magnetic resonance (NMR) studies confirmed the presence of solvents or solvent mixtures. Upon heating, these channel‐type cocrystals exhibit a thermosalient effect, with temperature regulation achieved by releasing pure or solvent mixtures. Differential scanning calorimetry and thermogravimetry (DSC–TGA) analyses revealed that the transition temperatures changed progressively, demonstrating controllable thermal actuation through the release of occluded solvents. This work demonstrates a simple yet powerful way to regulate mechanical responses in molecular crystals, thereby advancing the design of responsive energy conversion materials.

In this work, we report a detailed investigation on the factors affecting the in‐plane motion of tetrafluoro‐1,4‐benzoquinone (TFBQ) within a series of charge‐transfer (CT) cocrystals formed with various fused aromatic donors. Six crystalline materials were obtained, including four cocrystals, a polymorph, and a solid solution. These were characterized by single‐crystal X‐ray diffraction (SC XRD), solid‐state NMR, FTIR, UV‐Vis spectroscopy, and DFT calculations. All cocrystals exhibited short π‐stacking interactions and varied noncovalent interactions (NCI) modulating the in‐plane motion of TFBQ. ¹⁹ F T ₁ relaxation measurements allowed the quantification of the activation enthalpies ( ΔH ^‡ ) and entropies ( ΔS ^‡ ), with theoretical calculations backing these results. Cocrystal 4 is the solid with the most restricted motions due to the presence of strong hydrogen bonds. In contrast, cocrystal 3a depicts the highest in‐plane motional frequencies (up to 2.2 MHz at 300 K), owing to the weak contacts around TFBQ. Surprisingly, a solid solution ( 5 ), which resembled a mixture of cocrystals 2 and 3a , displayed no significant in‐plane motions, despite having similar packing and relaxation behavior to the binary cocrystals. This work illustrates how subtle variations in donor structure affect the in‐plane motions and photophysical properties of CT cocrystals, providing valuable insight into the rational design of functional materials.