Jia Li

Beyond the structural precision and design versatility of metal-organic frameworks (MOFs), dynamic MOFs responsive to external stimuli are emerging as programmable crystalline systems. Herein, two isostructural cobalt-based MOFs, [Co₂(L1)₂(L2)]_n (NBU-X4) and [Co₂(L1)₂(L3)]_n (NBU-X5), constructed from the ligands 3,3'-(9,9-diethyl-9H-fluorene-2,7-diyl)dibenzoic acid (H₂L1), 1,4-bis(4-pyridyl)naphthalene (L2), and 9,10-di(4-pyridyl)anthracene (L3), were synthesized to elucidate the interplay between ligand flexibility and framework rigidity. Single-crystal X-ray diffraction analyses reveal that NBU-X4 exhibits structural adaptability mediated by nonuniform ligand torsion, enabling a reversible single-crystal-to-single-crystal transformation between NBU-X4-1 and NBU-X4-2 that modulates its photothermal response. Steric hindrance in NBU-X5 suppresses torsional motion, resulting in a rigid framework. NBU-X5 achieves a maximum surface temperature of 316 °C within 10 s under 808 nm laser irradiation (1.6 W cm^-2) on the glass substrate. NBU-X4-1 and NBU-X4-2 exhibit durable photothermal cycling over 50 cycles at 0.2 W cm^-2 and maintain a consistent temperature gap, enabling memory-type photothermal sensing on an alumina substrate. These findings establish a clear structure-function correlation among ligand torsion, framework adaptability, and photothermal efficiency, offering a rational design strategy for dynamic MOF-based temperature-responsive materials.

A chemically stable Ni7-cluster-based MOF material with methyl-rich pore surfaces shows significant C ₂ H ₂ /C ₂ H ₄ and C ₃ H ₆ /C ₃ H ₈ separation by tuning pore environments via coordinating solvent molecules.

This study presents a stable Ni₇-cluster MOF with enhanced adsorption through pore microenvironment tuning. Two types of guest-free frameworks achieve C₂H₂/C₂H₄ separation, providing deep insights into separation mechanisms.

Multi-interpenetrated metal-organic frameworks (MOFs) have exhibited excellent performance in selective adsorption due to the variable post-interspersed flexibility, but the design and control remain challenging. Herein, two anthracene-based ligands, 4,4'-(anthracene-9,10-diyl)dibenzoic acid (H₂L1) and 9,10-di(pyridin-4-yl)anthracene (L2), are used to construct a new three-dimensional 6-fold interpenetrated MOF [Zn(L1)(L2)]_n (NBU-X1), which exhibits multiple C-H···π interactions that enhance the structural rigidity, thereby entangling with a C₂H₂/C₂H₄ separation performance. In this material, the incorporation of abundant anthracene rings within the framework not only partitions and restricts the pore window size to a quasi-double pore but also stabilizes it through host-host interactions. The structural stability upon heating or guest displacement/removal has been investigated by single-crystal X-ray diffraction and in situ variable-temperature powder X-ray diffraction, in contrast to the extreme flexibility of most multi-interpenetrated MOFs. The performance of purifying C₂H₄ from C₂H₂/C₂H₄ mixtures has been proved by dynamic breakthrough tests.

A novel Cl-decorated trinuclear-Cu cluster-based MOF (NbU-7-Cl, NbU denotes Ningbo University) was synthesized by a stepwise synthesis strategy. Compared to one-step reactions, the strategy of combining cationic templates with single-crystal-to-single-crystal transformation provides more possibilities for the design and postsynthetic modification of multifunctional materials. Note that the chloride ions are attached to the copper ions of the planar trinuclear cluster nodes in a fully symmetric or partially asymmetric manner. The insertion of the chloride ion can alter the overall symmetry and adsorption energy in addition to occupying the appropriate asymmetric orbit and reducing the effective active sites of metal. The activated NbU-7-Cl displays improved C2H2 uptake capacity and C2H2/C2H4 and C2H2/CO2 separation performance, which is proved by breakthrough experiments.

Surface and interface engineering, especially the creation of abundant Cu⁰/Cu⁺ interfaces and nanograin boundaries, is known to facilitate C₂₊ production during electrochemical CO₂ reductions over copper-based catalysts. However, precisely controlling the favorable nanograin boundaries with surface structures (e.g., Cu(100) facets and Cu[n(100)×(110)] step sites) and simultaneously stabilizing Cu⁰/Cu⁺ interfaces is challenging, since Cu⁺ species are highly susceptible to be reduced into bulk metallic Cu at high current densities. Thus, an in-depth understanding of the structure evolution of the Cu-based catalysts under realistic CO₂RR conditions is imperative, including the formation and stabilization of nanograin boundaries and Cu⁰/Cu⁺ interfaces. Herein we demonstrate that the well-controlled thermal reduction of Cu₂O nanocubes under a CO atmosphere yields a remarkably stable Cu₂O-Cu nanocube hybrid catalyst (Cu₂O(CO)) possessing a high density of Cu⁰/Cu⁺ interfaces, abundant nanograin boundaries with Cu(100) facets, and Cu[n(100)×(110)] step sites. The Cu₂O(CO) electrocatalyst delivered a high C₂₊ Faradaic efficiency of 77.4% (56.6% for ethylene) during the CO₂RR under an industrial current density of 500 mA/cm². Spectroscopic characterizations and morphological evolution studies, together with in situ time-resolved attenuated total reflection-surface enhanced infrared absorption spectroscopy (ATR-SEIRAS) studies, established that the morphology and Cu⁰/Cu⁺ interfacial sites in the as-prepared Cu₂O(CO) catalyst were preserved under high polarization and high current densities due to the nanograin-boundary-abundant structure. Furthermore, the abundant Cu⁰/Cu⁺ interfacial sites on the Cu₂O(CO) catalyst acted to increase the *CO adsorption density, thereby increasing the opportunity for C-C coupling reactions, leading to a high C₂₊ selectivity.

The detailed mechanism of metal-organic-framework (MOF)-based separation materials is still obscure, which obviously hinders their actual application. To address this problem, a trinuclear Cu-cluster-based MOF with a minimum metal-active plane was synthesized for the study of the very challenging C₂H₂/C₂H₄ and C₂H₂/CO₂ separations. Via dispersion-corrected density functional theory calculations, it is indicated that the difference of the adsorption energy accounts for the excellent separation properties toward C₂H₂/C₂H₄ and C₂H₂/CO₂ mixtures, while the frontier molecular orbitals demonstrate that the adsorption-energy difference originates from the orbital-symmetry difference of gas molecules. All of these results provide not only deep insight into the separation mechanism but also an alternative strategy to prepare efficient adsorbents.

We reported herein a new 3D bio-MOF (NbU-12) using a pore space partition strategy: MIL-88D was selected as a primary framework, and adenine connected two independent MIL-88D to form a self-interpenetrated structure. Because of this, the hexagonal channel in MIL-88D split into two small rectangular channels. Different from the reported series CPM-35 materials, NbU-12 simultaneously maximized the retention of open metal sites from MIL-88D and introduced a Watson–Crick face to the pore surface of NbU-12. Remarkably, NbU-12 exhibits an excellent selectivity performance toward C₂H₆/C₂H₄ and C₂H₆/CH₄, which was proven by ideal adsorbed solution theory calculation and breakthrough experiments.

A novel noninterpenetrated tetranuclear cobalt(II)-based metal–organic framework, (NH₄)₂·[Co₄(μ₃-OH)₂(ina)₂(pip)₃]·4EtOH·H₂O (simplified as NbU-10·S), constructed by mix linkers was synthesized by a hydrothermal method. Interestingly, the presence of a hydrophobic benzene ring in the organic linker makes NbU-10·S exhibit high stability in high temperature and even in aqueous solution over a wide pH range of about 4–13. Magnetic studies showed that the tetranuclear cobalt(II) units in NbU-10·S show dominant antiferromangetic properties. However, in the absence of Lewis basic functional sites and open metal sites in the material, NbU-10 still displays high C₂H₂/CO₂ and C₂H₂/C₂H₄ selectivity in ideal adsorbed solution theory calculations and dynamic breakthrough experiments. Moreover, density functional theory calculations were performed to identify the adsorption characteristics of different gas molecules.