Construction of saturated coordination titanium-based metal–organic framework for one-step C2H2/C2H6/C2H4 separation

Hierarchically porous MOF@COF structures with ultrafast gas diffusion rate for C2H6/C2H4 separation

For ethylene purification, C2H6-selective metal-organic frameworks (MOFs) show great potential to directly produce polymer-grade C2H4 from C2H6/C2H4 mixtures. Most C2H6-traping MOFs are ultra-microporous structures so as to strengthen multiple supramolecular interactions with C2H6. However, the narrowed pore channels of C2H6-traping MOFs cause large guest diffusion barriers, greatly hampering their practical applications. Herein, we present a feasible strategy by precisely constructing hierarchically porous MOF@COF core-shell structures to address this issue. Additional mesoporous diffusion channels were incorporated between MOF crystals through the construction of the COF shell, thereby enhancing the gas adsorption kinetics. Notably, designing a core-shell MOF@COF structure with an optimal coating amount of mesoporous COF shell will further improve the gas diffusion rate. Breakthrough experiments reveal that the tailored MOF@COF composites can effectively achieve C2H6/C2H4 separation and maintain its separation performance over five continuous measurement cycles. This investigation opens up a new avenue to solve the diffusion/transfer issues and provides more opportunities and potentials for MOF@COF composites in practical separation applications.

Advancing Pore-Space-Partitioned Metal-Organic Frameworks with Isoreticular Cluster Concept

Trigonal planar M3(O/OH) trimers are among the most important clusters in inorganic chemistry and are the foundational features of multiple high-impact MOF platforms. Here we introduce a concept called isoreticular cluster series and demonstrate that M3(O/OH), as the first member of a supertrimer series, can be combined with a higher hierarchical member (double-deck trimer here) to advance isoreticular chemistry. We report here an isoreticular series of pore-space-partitioned MOFs called M3M6 pacs made from co-assembly between M3 single-deck trimer and M3x2 double-deck trimer. Important factors were identified on this multi-modular MOF platform to guide optimization of each module, which enables the phase selection of M3M6 pacs by overcoming the formation of previously-always-observed same-cluster phases. The new pacs materials exhibit high surface area and high uptake capacity for CO2 and small hydrocarbons, as well as selective adsorption properties relevant to separation of industrially important mixtures such as C2H2/CO2 and C2H2/C2H4. Furthermore, new M3M6 pacs materials show electrocatalytic properties with high activity.

Metal-Organic Framework Featuring Cubic Caged Structures for One-Step Ethylene Purification from Ethylene/Ethane Mixtures

Separation of C2H6/C2H4 mixtures is of significant importance in the chemical industry but remains a challenge due to the physicochemical similarities of C2H6 and C2H4. Herein, a metal-organic framework (MOF), [Zn4(μ4-O)(PCTF)3]n (Zn-PCTF) (PCTF2-= 5-trifluoromethyl-1H-pyrazole-4-carboxylic), is provided for the removal of C2H6 from C2H6/C2H4 mixtures. Zn-PCTF displays a three-dimensional framework featuring one-dimensional pore channels with periodic bottleneck segments. The well-balanced C2H6 adsorption capacity (79.0 cm3 g-1 at 298 K) and C2H6/C2H4 selectivity (1.8) for Zn-PCTF under ambient conditions boost Zn-PCTF with highly promising potentials for efficient purification of C2H4 from C2H6/C2H4 mixtures, which is verified by the dynamic column breakthrough experiments. The well-matched caged pores and suitable pore chemistry (particularly the presence of abundant Lewis base sites (N, O, and F) on the pore surfaces) for C2H6 account for the high-performance C2H6/C2H4 separation of Zn-PCTF unveiled by computational simulations.

Cr(VI) and doxorubicin adsorptive capture by a novel bionanocomposite of Ti-MOF@TiO2 incorporated with watermelon biochar and chitosan hydrogel

Biodegradable polymers, biochars and metal organic frameworks (MOFs) have manifested as top prospects for elimination of harmful pollutants. In the current study, Ti-MOF was synthesized and decorated with TiO2 nanoparticles, then embedded into watermelon peel biochar and functionalized with chitosan hydrogel to produce Ti-MOF@TiO2@WMPB@CTH. Various instruments were employed to assure the effective production of the bionanocomposite. The HR-TEM and SEM studies referred to excellent surface porosity and homogeneity of Ti-MOF@TiO2@WMPB@CTH bionanocomposite, with 51.02-74.23 nm. Based on the BET analysis, the mesoporous structure has a significant surface area of 366.04 m2 g-1 and a considerable total pore volume of 11.38 × 10-2 cm3 g-1, with a mean pore size of 12.434 nm. Removal of doxorubicin (DOX) and hexavalent chromium (Cr(VI)) was examined under various experimentations. Pseudo-second order kinetic models in addition to Langmuir isotherm offered the best fitting. Thermodynamic experiments of the two contaminants demonstrated spontaneous and endothermic interactions. After five subsequent adsorption and desorption cycles, Ti-MOF@TiO2@WMPB@CTH bionanocomposite demonstrated an exceptional recyclability for the elimination of DOX and Cr(VI) ions, reaching 97.96 % and 95.28 %, respectively. Finally, the newly designed Ti-MOF@TiO2@WMPB@CTH bionanocomposite demonstrated a high removing efficiency of Cr(VI) ions and DOX from samples of real water.

Precise Pore Engineering of fcu-Type Y-MOFs for One-Step C2 H4 Purification from Ternary C2 H6 /C2 H4 /C2 H2 Mixtures

The purification of C2 H4 from C2 H6 /C2 H4 /C2 H2 mixtures is of great significance in the chemical industry for C2 H4 production but remains a daunting task. Guided by powerful reticular chemistry principles, herein a systematic study is carried out to engineer pore dimensions and pore functionality of fcu-type Y-based metal-organic frameworks (Y-MOFs) through the construction of a series of eight new structures using linear dicarboxylate linkers with different length and functional groups. This study illustrates how delicate changes in pore size and pore surface chemistry can effectively influence the adsorption preference of C2 H6 , C2 H4 , and C2 H2 by the MOFs. Importantly, clear relations between pore size/pore surface polarity and C2 adsorption selectivities of this series of MOFs are established. In particular, HIAM-326 built on a linker decorated with trifluoromethoxy group shows notably preferential adsorption of C2 H6 and C2 H2 over C2 H4 , with balanced C2 H2 /C2 H4 and C2 H6 /C2 H4 selectivities. This endows the compound with the capability of one-step purification of C2 H4 from C2 H6 /C2 H4 /C2 H2 ternary mixtures, which is validated by breakthrough measurements where high purity C2 H4 (99.9%+) can be obtained directly from the separation column. Its adsorption thermodynamics and underlying selective adsorption mechanisms are further revealed by ab initio calculations.

Separation of C2H2/C2H4/C2H6 and C2H2/CO2 in a Nitrogen-Rich Copper-Based Microporous Metal-Organic Framework

The purification of industrially valuable C2H2 and C2H4 from multicomponent mixtures represents a crucial process in the chemical industry. In this study, we present a copper-based metal-organic framework (L-py-Cu) built on a nitrogen-rich organic linker that is capable of separating C2H2/C2H4/C2H6 and C2H2/CO2 mixtures, therefore producing highly pure C2H4 and C2H2, respectively. L-py-Cu exhibits favorable adsorption of C2H2 and C2H6 over C2H4 and thus achieves one-step C2H4 purification from C2H2/C2H4/C2H6 ternary mixtures, as verified by multicomponent breakthrough measurements. In addition, it can also extract C2H2 from C2H2/CO2 binary mixtures.

Pillar-layer Zn-triazolate-dicarboxylate frameworks with a customized pore structure for efficient ethylene purification from ethylene/ethane/acetylene ternary mixtures

The selective adsorption of C₂H₆ and C₂H₂ over C₂H₄ from C₂H₂/C₂H₄/C₂H₆ ternary mixtures for one-step C₂H₄ purification represents a crucial yet challenging task in industry. The pore structure of the adsorbents must be finely tailored to meet the demanding requirements for the separation considering the very similar physicochemical properties of the three gases. Herein, we report a Zn-triazolate-dicarboxylate framework, HIAM-210, featuring a novel topology which possesses one-dimensional channels decorated with adjacent uncoordinated carboxylate-O atoms. The suitable pore size and customized pore environment enable the compound to selectively capture C₂H₆ and C₂H₂ with high C₂H₂/C₂H₄ and C₂H₆/C₂H₄ selectivities of both 2.0. Breakthrough experiments show that polymer-grade C₂H₄ can be directly harvested from C₂H₂/C₂H₄/C₂H₆ (34/33/33 and 1/90/9) ternary mixtures. The underlying mechanism of the preferential adsorption was uncovered by grand canonical Monte Carlo simulations and DFT calculations.

Customizing Metal-Organic Frameworks by Lego-Brick Strategy for One-Step Purification of Ethylene from a Quaternary Gas Mixture

One-step purification of ethylene (C₂ H₄ ) from a quaternary gas mixture of C₂ H₆ /C₂ H₄ /C₂ H₂ /CO₂ by adsorption is a promising separation process, yet developing adsorbents that synergistically capture various gas impurities remains challenging. Herein, a Lego-brick strategy is proposed to customize pore chemistry in a unified framework material. The ethane-selective MOF platform is further modified with customized binding sites to specifically adsorb acetylene and carbon dioxide, thus one-step purification of C₂ H₄ with high productivity of polymer-grade product (134 mol kg^-1 ) is achieved on the assembly of porous coordination polymer-2,5-furandicarboxylic acid (PCP-FDCA) and PCP-5-aminoisophthalic acid (IPA-NH₂ ). Computational studies verify that the low-polarity surface of this MOFs-based platform provides a delicate environment for C₂ H₆ recognition, and the specific binding sites (FDCA and IPA-NH₂ ) exhibit favorable trapping of C₂ H₂ and CO₂ via CH^δ+ ···O^δ- and C^δ+ ···N^δ- electrostatic interactions, respectively. The proposed Lego-brick strategy to customize binding sites within the MOFs structure provides new ideas for the design of adsorbents for compounded separation tasks.

Synergistic binding sites in a hybrid ultramicroporous material for one-step ethylene purification from ternary C2 hydrocarbon mixtures

One-step separation of C₂H₄ from ternary C₂H₂/C₂H₄/C₂H₆ hydrocarbon mixtures is of great significance in the industry but is challenging due to the similar sizes and physical properties of C₂H₂, C₂H₄, and C₂H₆. Here, we report an anion-pillared hybrid ultramicroporous material, CuTiF₆-TPPY, that has the ability of selective recognition of C₂H₄ over C₂H₂ and C₂H₆. The 4,6-connected fsc framework of CuTiF₆-TPPY exhibits semi-cage-like one-dimensional channels sustained by porphyrin rings and TiF₆^2- pillars, which demonstrates the noticeably enhanced adsorption of C₂H₂ and C₂H₆ over C₂H₄. Dynamic breakthrough experiments confirm the direct and facile high-purity C₂H₄ (>99.9%) production from a ternary gas mixture of C₂H₂/C₂H₆/C₂H₄ (1/9/90, v/v/v) under ambient conditions. Computational studies and in situ infrared reveal that the porphyrin moieties with large π-surfaces form multiple van der Waals interactions with C₂H₆; meanwhile, the polar TiF₆^2- pillars form C-H•••F hydrogen bonding with C₂H₂. In contrast, the recognition sites for C₂H₄ in the framework are less marked.

Linker micro-regulation of a Hofmann-based metalorganic framework for efficient propylene/propane separation

Fabricating easily available adsorbents with highly selective adsorption separation performance for propylene/propane mixtures is a desirable and energy-efficient way to produce high-purity propylene in the petrochemical industry. In this study,...

General pore features for one-step C2H4 production from C2 hydrocarbon mixture

Herein we proposed the required general pore features for one-step C2H4 production from C2 hydrocabon mixture: (i) non-metallic binding site; (ii) polar pore surface; (iii) narrow pocket. Four representative MOFs...

Lanthanide-Organic Frameworks Featuring Three-Dimensional Inorganic Connectivity for Multipurpose Hydrocarbon Separation

Implementation of lanthanide-organic frameworks (LOFs) as solid adsorbents has been frequently handicapped by their permanent porosity being difficult to establish owing to the remarkable flexibility and diversity of lanthanide ions in terms of coordination number and geometry. Construction of robust LOFs with permanent porosity for industrially important hydrocarbon separation will greatly expand their application potential. In this work, by distributing N and O donors into an m-terphenyl skeleton, we rationally synthesized a heterofunctional linker, and constructed a pair of isostructural LOFs. Due to the inclusion of a rarely observed three-dimensional metal-carboxylate backbone serving as a highly connected inorganic secondary building unit, their permanent porosities were successfully established by diverse gas isotherms. They can be applied as separating media not only for natural gas purification and removal of carbon dioxide from C₂ hydrocarbons but also more importantly for single-step ethylene (C₂H₄) purification from a three-component C₂H_n mixture during the adsorption process. The latter separation is very challenging and has been less reported in the literature. This work provides a unique example of LOFs featuring three-dimensional inorganic connectivity applied to multipurpose hydrocarbon separations.

Confined Ionic Liquid-Built Gas Transfer Pathways for Efficient Propylene/Propane Separation

The separation of light olefins from paraffins using membrane technology is highly desired; however, synthetic polymer membranes generally suffer a pernicious trade-off between permeability and selectivity. Herein, we show that this limitation can be overcome by constructing selective gas transfer pathways in a polymer matrix, as demonstrated by incorporating composites of ionic liquids and zeolitic imidazolate frameworks (ZIFs) to form mixed-matrix membranes. Using propylene/propane separation as a model system, dramatic improvements in the propylene permeability of 218.4 Barrer and propylene/propane separation factor of 45.7 were achieved compared to the values obtained using individual components as a filler. The synergy between the high solubility of the gas molecules in ionic liquids and the size screening ability of ZIF exacerbates the difference in the transmission of propylene and propane, thus leading to superior separation performance. This work presents a promising strategy for the design of membranes for efficient gas separation.