Achieving efficient adsorption and separation of C2H2/CO2 mixtures is a goal that people have always pursued to improve the situation of high energy consumption brought by traditional separation technologies in industry today. High-nuclearity metal cluster-based MOFs with different functionalities are promising for this separation, but it is a complicated and difficult task to precisely control their structures. The strategy of pore-space partition (PSP) is a powerful way to construct this type MOFs, which has the characteristic of isostructural relationship, and can be resulted in a similar performance for them. Therefore, it is an interesting work to explore the effect of MOFs property by adjusting the size of PSP dividers. Herein, three tetranuclear Cu(II) cluster-based MOFs (FJU-112/113/114) with dual functionalities has been successfully obtained by PSP strategy with various lengths of divider units. With the highest microporosity and unique functional site, FJU-114 realized a good improvement in the adsorption and separation performance of C2H2/CO2. The gas adsorption and lab-scale C2H2/CO2 breakthrough experiments demonstrated that FJU-114 exhibits the highest adsorption uptake of 77 cm3/g for C2H2, and shows the best separation factor of 4.2 among three MOFs. The GCMC simulation reveals that a stronger adsorption binding site of C2H2 in FJU-114a located in the cage II near the unchanged tetranuclear copper node, combined with its high microporosity to achieve the effect of dual functionalities for the improvement performance of C2H2 adsorption and separation.

Tautomers coexisting in an equilibrium system have significant potential for regulating luminescent properties because of their structural differences. However, separating and stabilizing tautomers at room temperature is a considerable challenge. In this study, it is found that hydrogen-bonded organic frameworks (HOFs) composed of Br- anions can effectively separate and stabilize two proton-transfer tautomers of triarylformamidinium bromide: namely, the nitrogen cation (BA-N) and carbon cation (BA-C). The BA-N crystal consisting of a dense anionic HOF and parallelly aligned organic cations exhibits green thermally activated delayed fluorescence and red room-temperature phosphorescence (RTP). The BA-C crystal contains acetone molecules that induce an antiparallel arrangement of the organic cations to form a loose HOF, producing blue prompt fluorescence and green RTP. Interestingly, switching of the HOFs between BA-N and BA-C can be achieved through the uptake and release of acetone, thereby dynamically adjusting multiple luminescent properties. Consequently, the HOF crystals can be used for the highly sensitive and specific sensing of acetone with a detection limit of 66.74 ppm. This study not only stabilizes tautomeric luminescent materials at room temperature, but also provides a new method for constructing smart HOFs with a sensitive response to a stimulus.

Hydrogen-bonded organic frameworks (HOFs) are a promising candidate for optical sensing, but the lack of effective design strategies poses significant challenges to the construction of HOFs for organic acid sensing. In this work, the first HOF for organic acid sensing is reported by constructing a multiple-pyridine carbazole-based dense HOF, namely HOF-FJU-206, from a tripyridine-carbazole molecular 3,6-bis(pyridin-4-yl)-9-(4-(pyridin-4-yl)phenyl)-9H-carbazole (CPPY) with carbazole center for luminescence, pyridyl sites for its responsive of hydrogen proton, and narrow channels in the dense framework for the diffusion of hydrogen protons. HOF-FJU-206 exhibits differential responsively fluorescence sensing and recovery properties to formic, acetic, and propionic acids with different molecular sizes and pKa value (acid dissociation constant). The dissociation degree of various acids can be determined by analyzing the slope of changes in both peak wavelength and intensity of in-situ fluorescence, which easily enables the dual-corrective recognition of different acids. The varying degree of protonation at pyridine sites is proved to be the reason for differential sensing of various acids, as demonstrated by 1H NMR spectra, X-ray photoelectron spectroscopy (XPS) characterization, and modeling studies.

Flexible-robust hydrogen-bonded organic frameworks (HOFs) are attracting increasing interest due to their excellent separation performance for important industrial gases, but the construction remains challenging. Herein, a sticked-layer strategy is first proposed to construct a flexible-robust HOF, HOF-FJU-8, from a donor (D)-pi-acceptor (A) molecule 4,4',4 '',4'''-(pyrrolo[3,2-b]pyrrole-1,2,4,5-tetrayl)tetrabenzonitrile (DP-4CN). HOF-FJU-8 is a microporous three-dimensional framework composed of two kinds of DP-4CN molecules, one acting as building units for the two-dimensional layer via C N center dot center dot center dot H-C hydrogen bond dimers and another as the sticks to link the layers along channels through D-A pi center dot center dot center dot pi interactions. The activated framework HOF-FJU-8a possesses flexible-robust pore characteristics, as determined by the gas adsorption and in situ gas-loaded powder X-ray diffraction. HOF-FJU-8a exhibits adaptive adsorption and stronger binding affinity to C2H2 rather than CO2 due to the flexible-robust nature, which can effectively separate acetylene and carbon dioxide mixtures. [GRAPHICS] .

The separation of propylene (C 3 H 6 ) and propane (C 3 H 8 ) is of great significance in the chemical industry, which poses a challenge due to their almost identical kinetic diameters and similar physical properties. In this work, we synthesized an ultramicroporous flexible hydrogen-bonded organic framework (named HOF-FJU-106) by using molecule 2,3,6,7-tetra (4-cyanophenyl) tetrathiafulvalene (TTF-4CN). The formation of the dimer causes the TTF-4CN molecular to bend and weaken π-stacked interactions, coupled with the flexibility of C≡N H−C hydrogen bonds, which leads to reversible conversion between open and closed frameworks through the mutual slip of adjacent layers/columns under activation and stimulation of gas molecules. Through gas adsorption isotherms and adsorption enthalpy, HOF-FJU-106a exhibited adaptive adsorption and stronger binding affinity for C 3 H 6, and presented a recorded gas uptake ratio of C 3 H 6 /C 3 H 8 (23.77) among presentative HOF materials at room temperature to date. Importantly, the flexible HOF-FJU-106a shows an interesting phenomenon about the reversible gate pressure control under variable temperature, which realized the gas adsorption and separation performance enhancement for the binary C 3 H 6 /C 3 H 8 mixtures. This strategy through designing HOFs with thermoregulatory gating effect is a powerful way to maximize the performance of materials.

The performance of perovskite solar cells (PSCs) is often constrained by significant open-circuit voltage (V-OC) losses attributed to non-radiative recombination processes induced by detrimental trap states. Surface treatments using passivating ligands typically involve single active binding sites on perovskite, posing challenges for effective passivation. Here, an aromatic donor-acceptor (D-A) configured phthalocyanine treatment is proposed to aim at dual-site passivation of uncoordinated lead ions and effective mitigation of shallow and deep-level defects on the perovskite surface. The resulting benign p-type surface facilitates a more favorable energy level alignment and reduces energetic mismatches at the perovskite/Spiro-OMeTAD interface. Pc-BTBC, with its aromatic D-A configuration, demonstrated compatibility with various perovskite compositions. Optimized PSCs achieves a power conversion efficiency (PCE) of 25.15% and reduces the V-OC deficit to 0.379 V. Furthermore, encapsulated devices exhibited enhanced stability under damp-heat conditions (ISOS-D-2, 50% RH, 65 degrees C) with a T-92 of 1000 h and maintained maximum power point tracking under continuous light in ambient air at 65 degrees C (ISOS-L-2). Notably, fabricated wide-bandgap semitransparent PSCs (ST-PSCs) achieved a PCE of 20.29%, while four-terminal perovskite/silicon tandem solar cells (4T-P/STSCs) demonstrated an efficiency of 29.38%. This study provides insights into minimizing V-OC losses and represents significant progress toward commercializing perovskite photovoltaics.

Reticular chemistry and pore engineering have garnered significant advancements in metal-organic frameworks and covalent organic frameworks, leveraging robust metal-coordination and covalent bonds. However, these achievements remain elusive in hydrogen-bonded organic frameworks, hindered by their inherent weakness in hydrogen bonding. Herein, we strategically manipulate the porosity of hydrogen-bonded frameworks through a grafting approach, culminating in the synthesis of two isomorphic HOFs, HOF-FJU-99 and HOF-FJU-100, with distinct pore environments. Remarkably, HOF-FJU-100, with its microporous architecture, not only showcases exceptional stability but also achieves unparalleled separation efficiency and ultrahigh selectivity for C2H2/CO2 mixtures (50/50, v/v) under ambient conditions. Its IAST selectivity value of 201 stands as a benchmark, towering over all previously reported HOFs. The pore of HOF-FJU-100 boasts an electrostatic potential highly favourable for C2H2 adsorption, as evidenced by single crystal X-ray diffraction analysis revealing multiple hydrogen bonding interactions between C2H2 molecules and the framework. In situ gas-carrier powder X-ray diffraction analysis underscores the adaptability of pore structure, dynamically adjusting its orientation in response to C2H2, thereby enabling a highly efficient and specific separation of C2H2/CO2 mixtures through specific adsorptive interactions.

Directional control of photon transport at micro/nanoscale holds great potential in developing multifunctional optoelectronic devices. Here, the switchable anisotropic/isotropic photon transport is reported in a double-dipole metal-organic framework (MOF) based on radical-controlled energy transfer. Double-dipole MOF microcrystals with transition dipole moments perpendicular to each other have been achieved by the pillared-layer coordination strategy. The energy transfer between the double dipolar chromophores can be modulated by the photogenerated radicals, which permits the in situ switchable output on both polarization (isotropy/anisotropy state) and wavelength information (blue/red-color emission). On this basis, the original MOF microcrystal with isotropic polarization state displays the isotropic photon transport and similar reabsorption losses at various directions, while the radical-affected MOF microcrystal with anisotropic polarization state shows the anisotropic photon transport with distinct reabsorption losses at different directions, finally leading to the in situ switchable anisotropic/isotropic photon transport. These results offer a novel strategy for the development of MOF-based photonic devices with tunable anisotropic performance.

Organic crystals have emerged as a promising platform for designing luminescent materials; yet, achieving tuneable fluorescence through subtle structural changes remains exceptionally rare. In this work, we report the fluorescence modulation caused by subtle structural changes in a solvent-free framework, HOF-FJU-101, assembled by a D-A molecule 3,4-bis(bis(4-bromophenyl)amino)cyclobut-3-ene-1,2-dione (o-SQDPA-Br). HOF-FJU-101 is a dense hydrogen-bonded organic framework interconnected through hydrogen bonding, pipi interactions, and conjugation between bromine atoms and benzene rings. Switching the crystallization mother liquor from dimethyl sulfoxide to dichloromethane, acetone, and N,N-dimethylformamide, different isomorphism HOF-FJU-101 crystals were obtained with subtle structure changes in both intermolecular Br4Ph C and intramolecular C27-Br4 distances due to the contraction deformation of heavy atom Br, which affects the electron transfer from diphenylamine donor to the squaric acid ring acceptor, resulting in significantly differentiated luminescence behavior. The tuneable emission wavelength range extended from 651 to 604 nm, with a maximum of up to 47 nm shifts.

Stimulus-responsive hydrogen-bonded organic frameworks (HOFs) can respond to specific physical or chemical stimuli by exhibiting reversible changes in structure, conductivity, color and luminescence, along with the inherent characteristics of HOFs such as simple composition, flexibility and metal-free, which together contribute to the widespread application of stimulus-responsive HOF materials in photoconductivity, chromism, fluorescence sensing, drug delivery, gas adsorption and separation. This review provides a summary of the construction strategies for stimulus-responsive HOFs, categorically reviews various stimulus-responsive HOFs based on different stimuli for the first time, briefly elucidates their applications across various fields, and concludes by emphasizing their advantages and the challenges they face.

It has been widely accepted that acidic species, such as HCl, inhibit the polymerization process of N-carboxyanhydrides (NCAs), which have to be removed to guarantee the successful synthesis of polypeptides. Herein, we showed that the im-pact of organic acids on NCA polymerization was dependent on their pKa values in dichloromethane. While stronger acids like trifluoroacetic acids completely blocked the chain propagation as expected, weaker acids such as acetic acids accel-erated the polymerization rate instead. The addition of acids not only protonated the propagating amino groups but also activated NCA monomers, whose balance determined the catalytic or inhibitory effect. Additionally, the acid-catalyzed polymerization exhibited one-stage kinetics that differed from conventional cooperative covalent polymerizations, result-ing in excellent control over molecular weights even with an accelerated rate. The pKa-dependence inspired us to turn the inhibitory acids into catalysts on demand, promoting the controlled polymerization from non-purified NCA monomers. This work highlights the possibility to change the conventional understanding of a catalyst/inhibitor by altering reaction conditions, which not only sheds light on the design of new catalysts, but also offers a practical strategy to prepare poly-peptide materials in an efficient and controlled manner.

Efficient conversion of glycerol to 1,3-dihydroxyacetone (DHA) is the affirmation and guarantee of the feasible development of biodiesel industry, but the biocompatibility of catalyst must be considered due to the wide application of DHA in food and medicine industries. In this work, an environmentally benign biosynthesis approach with Syringa oblata Lindl. (SoL) leaf extract was employed to fabricate Au/CuO catalysts for the oxidation of glycerol to DHA. The biosynthesized SoL-Au/CuO catalysts were characterized and the effects of plant extracts concentration, gold loading, calcination temperature and reaction conditions on the catalytic performance were systematically analyzed. High catalytic performance with glycerol conversion rate of 95.7% and DHA selectivity of 77.9% can be attained under optimum conditions. This work provides the first example of preparing biocompatible catalyst for the thermal catalytic oxidation of glycerol to DHA, which can not only reach efficient conversion of glycerol and selectivity to DHA, but also is simple, green, environmentally friendly, and promising.

The development of porous adsorbents to address the trade-off between physical adsorption capacity and selectivity has attracted extensive research interest due to their potential applications in gas separation and purification, but remains a daunting challenge. Herein, we report a new strategy involving increasing connected numbers of external linkers (from di-connected DCM to tri-connected TCM) to crosslink nitrogen-rich carbazole derivatives, thereby improving the microporosity of microporous polycarbozole frameworks and promoting CO2 adsorption capacity and selectivity. This is mainly attributed to tri-connected linker can make carbazole-based monomers more closely packed than di-connected linker, resulting in higher microporosity in tri-connected polymers constructed from the same monomer than that of di-connected polymers. Meanwhile, the dynamic breakthrough experiments show that tri-connected polymers have better CO2/N2 separation abilities than diconnected polymers.

The efficient separation of xenon (Xe) and krypton (Kr) mixtures is a valuable but challenging process in the gas industry. Hydrogen-bonded organic frameworks (HOFs) have emerged as a promising class of porous materials for gas separation; however, due to the lack of available design methods, accurately adjusting the pore size of HOFs to improve the separation performance remains a major challenge. Herein, we present a pore engineering optimized strategy by enlarging the core size of the rigid monomers to increase the pore size of benzene cyanide-based HOFs. The replacement of the benzene ring in the molecular core of HOF-40 with a larger-sized dipyrrole ring resulted in the assembly of HOF-FJU-8a with a slightly larger pore size of 4.2 x 4.6 angstrom 2, which is demonstrated as the highest performing HOF material for Xe/Kr separation reported to date. The superior Xe/Kr separation was determined by the gas adsorption and dynamic breakthrough experiments, showing a separation factor of 8.5 and a Kr productivity over 72 L kg-1 from the binary Xe/Kr mixture. The tailored pore size of HOF-FJU-8a played a crucial role in enabling the significant differential host-guest interactions and binding affinity, as confirmed by the single crystal structures of Xe-or Kr-loaded HOF-FJU-8a and GCMC calculations. A pore engineering optimized strategy by enlarging the core size of rigid monomers is proposed to increase the pore size of benzene cyanide-based HOFs, resulting in the highest performing HOF material for Xe/Kr separation.

Rational design of high nuclear copper cluster-based metal-organic frameworks has not been established yet. Herein, we report a novel MOF (FJU-112) with the ten-connected tetranuclear copper cluster [Cu4(PO3)2(μ2-H2O)2(CO2)4] as the node which was capped by the deprotonated organic ligand of H4L (3,5-Dicarboxyphenylphosphonic acid). With BPE (1,2-Bis(4-pyridyl)ethane) as the pore partitioner, the pore spaces in the structure of FJU-112 were divided into several smaller cages and smaller windows for efficient gas adsorption and separation. FJU-112 exhibits a high separation performance for the C2H2/CO2 separation, which were established by the temperature-dependent sorption isotherms and further confirmed by the lab-scale dynamic breakthrough experiments. The grand canonical Monte Carlo simulations (GCMC) studies show that its high C2H2/CO2 separation performance is contributed to the strong π-complexation interactions between the C2H2 molecules and framework pore surfaces, leading to its more C2H2 uptakes over CO2 molecules.

It is challenging to achieve high-purity acetylene (C2H2) from the methylene (CH4) and carbon dioxide (CO2), due to their similar molecular structure and physical properties. Adsorption utilized porous materials, such as metal-organic frameworks (MOFs), has been considered as cost- and energy-efficient technology to separate acetylene mixtures. Herein, we reported a highly stable MOF, [Zn6L4(Me2NH2+)4 ‧3H2O] (named FJU-83), featuring T-shaped functional capture sites explored for acetylene capture and separation. In addition, FJU83a exhibits not only a high C2H2 uptake capacity of 122.9 cm3/g at 273 K, 1 bar, but also good C2H2/CH4 and C2H2/CO2 selectivity of 24 and 2.9 under moderate temperature and 1 bar, respectively. The high separation efficiency of the C2H2/CH4 and C2H2/CO2 are validated by dynamic fixed bed breakthrough experiments. The single crystal X-ray diffraction studies and Hirshfeld surface analysis revealed that T-type aromatic sites of FJU83a can separate C2H2 from CH4 and CO2 through multiple C-H & BULL;& BULL;& BULL;& pi; and & pi;& BULL;& BULL;& BULL;& pi; interactions.

The separation of acetylene (C 2 H 2 ) from carbon dioxide (CO 2 ) is a very important but challenging task due to their similar molecular dimensions and physical properties. In terms of porous adsorbents for this separation, the CO 2 -selective porous materials are superior to the C 2 H 2 -selective ones because of the cost- and energy-efficiency but have been rarely achieved. Herein we report our unexpected discovery of the first hydrogen bonded organic framework (HOF) constructed from a simple organic linker 2,4,6-tri(1 H -pyrazol-4-yl)pyridine (PYTPZ) (termed as HOF-FJU-88) as the highly CO 2 -selective porous material. HOF-FJU-88 is a two-dimensional HOFs with a pore pocket of about 7.6 Å. The activated HOF-FJU-88 takes up a high amount of CO 2 (59.6 cm 3  g −1 ) at ambient conditions with the record IAST selectivity of 1894. Its high performance for the CO 2 /C 2 H 2 separation has been further confirmed through breakthrough experiments, in situ diffuse reflectance infrared spectroscopy and molecular simulations.

The separation of C 2 H 2 /CO 2 is not only industrially important for acetylene purification but also great scientific challenge due to their very similar molecular size and physical properties. To address this difficulty, herein, we present an ultramicroporous hydrogen-bonded organic framework (HOF-FJU-1) from tetracyano bicarbazole to separate C 2 H 2 from CO 2 by taking advantage of differences in their electrostatic potential distribution. This material possesses a suitable pore environment and electrostatic potential distribution fitting well to C 2 H 2 , thus showing extra strong affinity to C 2 H 2 (46.73 kJ mol −1 ) and the highest IAST selectivity of 6675 for C 2 H 2 /CO 2 separation among the adsorbents reported. The single crystal X-ray diffraction reveals that the suitable pore environment in HOF-FJU-1 provides multiple C−H⋅⋅⋅π and hydrogen-bonded interactions N⋅⋅⋅H−C with C 2 H 2 molecules. Dynamic breakthrough experiments demonstrate its outstanding separation performance to C 2 H 2 /CO 2 mixtures.

Stimuli-responsive materials can respond to external effects, and proton transport is widespread and plays a key role in living systems, making stimuli-responsive proton transport in artificial materials of particular interest to researchers due to its desirable application prospects. On the basis of the rapid growth of proton-conducting porous metal-organic frameworks (MOFs), switched proton-conducting MOFs have also begun to attract attention. MOFs have advantages in crystallinity, porosity, functionalization, and structural designability, and they can facilitate the fabrication of novel switchable proton conductors and promote an understanding of the comprehensive mechanisms. In this Perspective, we highlight the current progress in the rational design and fabrication of stimuli-responsive proton-conducting MOFs and their applications. The dynamic structural change of proton transfer pathways and the role of trigger molecules are discussed to elucidate the stimuli-responsive mechanisms. Subsequently, we also discuss the challenges and propose new research opportunities for further development.

Rational design of hydrogen-bonded organic frameworks (HOFs) with multiple functionalities is highly sought after but challenging. Herein, we report a multifunctional HOF (HOF-FJU-2) built from 4,4',4'',4'''-(9H-carbazole-1,3,6,8-tetrayl)tetrabenzaldehyde molecule with tetrabenzaldeyde for their H bonding interactions and carbazole N-H site for its specific recognition of small molecules. The Lewis acid N-H sites allow HOF-FJU-2 facilely separate acetone from its mixture with another solvent like methanol with smaller pKa value. The donor (D)-π-acceptor (A) aromatic nature of the organic building molecule endows this HOF with solvent dependent luminescent/chromic properties, so the column acetone/methanol separation on HOF-FJU-2 can be readily visualized.