Effect of Polymorphism on the Sorption Properties of a Flexible Square-Lattice Topology Coordination Network

The stimulus-responsive behavior of coordination networks (CNs), which switch between closed (nonporous) and open (porous) phases, is of interest because of its potential utility in gas storage and separation. Herein, we report two polymorphs of a new square-lattice (sql) topology CN, X-sql-1-Cu, of formula [Cu(Imibz)2]n (HImibz = {[4-(1H-imidazol-1-yl)phenylimino]methyl}benzoic acid), isolated from the as-synthesized CN X-sql-1-Cu-(MeOH)2·2MeOH, which subsequently transformed to a narrow pore solvate, X-sql-1-Cu-A·MeOH, upon mild activation (drying in air or heating at 333 K under nitrogen). X-sql-1-Cu-A·MeOH contains MeOH in cavities, which was removed through exposure to vacuum for 2 h, yielding the nonporous (closed) phase X-sql-1-Cu-A. In contrast, a more dense polymorph, X-sql-1-Cu-B, was obtained by exposing X-sql-1-Cu-(MeOH)2·2MeOH directly to vacuum for 2 h. Gas sorption studies conducted on X-sql-1-Cu-A and X-sql-1-Cu-B revealed different switching behaviors to two open phases (X-sql-1-Cu·CO2 and X-sql-1-Cu·C2H2), with different gate-opening threshold pressures for CO2 at 195 K and C2H2 at 278 K. Coincident CO2 sorption and in situ powder X-ray diffraction studies at 195 K revealed that X-sql-1-Cu-A transformed to X-sql-1-Cu-B after the first sorption cycle and that the CO2-induced switching transformation was thereafter reversible. The results presented herein provide insights into the relationship between two polymorphs of a CN and the effect of polymorphism upon gas sorption properties. To the best of our knowledge, whereas sql networks such as X-sql-1-Cu are widely studied in terms of their structural and sorption properties, this study represents only the second example of an in-depth study of the sorption properties of polymorphic sql networks.

Shape-Memory Effect Enabled by Ligand Substitution and CO2 Affinity in a Flexible SIFSIX Coordination Network

We report that linker ligand substitution involving just one atom induces a shape-memory effect in a flexible coordination network. Specifically, whereas SIFSIX-23-Cu, [Cu(SiF6 )(L)2 ]n , (L=1,4-bis(1-imidazolyl)benzene, SiF6 2- =SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX-23-CuN , [Cu(SiF6 )(LN )2 ]n (LN =2,5-bis(1-imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO2 . As-synthesized SIFSIX-23-CuN , α, transformed to less open, γ, and closed, β, phases during activation. β did not adsorb N2 (77 K), rather it reverted to α induced by CO2 at 195, 273 and 298 K. CO2 desorption resulted in α', a shape-memory phase which subsequently exhibited type-I isotherms for N2 (77 K) and CO2 as well as strong performance for separation of CO2 /N2 (15/85) at 298 K and 1 bar driven by strong binding (Qst =45-51 kJ/mol) and excellent CO2 /N2 selectivity (up to 700). Interestingly, α' reverted to β after re-solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX-23-CuN .

Optimizing Sieving Effect for CO2 Capture from Humid Air Using an Adaptive Ultramicroporous Framework

Excessive CO2 in the air can not only lead to serious climate problems but also cause serious damage to humans in confined spaces. Here, a novel metal-organic framework (FJI-H38) with adaptive ultramicropores and multiple active sites is prepared. It can sieve CO2 from air with the very high adsorption capacity/selectivity but the lowest adsorption enthalpy among the reported physical adsorbents. Such excellent adsorption performances can be retained even at high humidity. Mechanistic studies show that the polar ultramicropore is very suitable for molecular sieving of CO2 from N2 , and the distinguishable adsorption sites for H2 O and CO2 enable them to be co-adsorbed. Notably, the adsorbed-CO2 -driven pore shrinkage can further promote CO2 capture while the adsorbed-H2 O-induced phase transitions in turn inhibit H2 O adsorption. Moreover, FJI-H38 has excellent stability and recyclability and can be synthesized on a large scale, making it a practical trace CO2 adsorbent. This will provide a new strategy for developing practical adsorbents for CO2 capture from the air.

Reversible transformations between the non-porous phases of a flexible coordination network enabled by transient porosity

Flexible metal-organic materials that exhibit stimulus-responsive switching between closed (non-porous) and open (porous) structures induced by gas molecules are of potential utility in gas storage and separation. Such behaviour is currently limited to a few dozen physisorbents that typically switch through a breathing mechanism requiring structural contortions. Here we show a clathrate (non-porous) coordination network that undergoes gas-induced switching between multiple non-porous phases through transient porosity, which involves the diffusion of guests between discrete voids through intra-network distortions. This material is synthesized as a clathrate phase with solvent-filled cavities; evacuation affords a single-crystal to single-crystal transformation to a phase with smaller cavities. At 298 K, carbon dioxide, acetylene, ethylene and ethane induce reversible switching between guest-free and gas-loaded clathrate phases. For carbon dioxide and acetylene at cryogenic temperatures, phases showing progressively higher loadings were observed and characterized using in situ X-ray diffraction, and the mechanism of diffusion was computationally elucidated.

Flexible metal-organic frameworks for gas storage and separation

Flexible metal-organic frameworks (MOFs) have gradually attracted much attention due to their reversible structural changes and flexible structural responses. The basic research of flexible MOFs is to study their dynamic responses under different external stimuli and translate the responses into applications. Most research studies on flexible MOFs focus on gas storage and separation, but lack a systematic summary. Here, we review the development of flexible MOFs, the structural transformation under the external effects of temperature, pressure, and guest molecules, and their applications in gas storage and separation. Microporous MOFs with flexible structures provide unique opportunities for fine-tuning their performance because the pore shape and size can be controlled by external stimuli. The characteristics of breathing phenomena and large specific surface area make flexible MOFs suitable candidates for gas storage and separation. Finally, the application prospects of flexible MOFs are reported.

Hysteresis curves reveal the microscopic origin of cooperative CO2 adsorption in diamine-appended metal-organic frameworks

Diamine-appended metal-organic frameworks (MOFs) of the form Mg₂(dobpdc)(diamine)₂ adsorb CO₂ in a cooperative fashion, exhibiting an abrupt change in CO₂ occupancy with pressure or temperature. This change is accompanied by hysteresis. While hysteresis is suggestive of a first-order phase transition, we show that hysteretic temperature-occupancy curves associated with this material are qualitatively unlike the curves seen in the presence of a phase transition; they are instead consistent with CO₂ chain polymerization, within one-dimensional channels in the MOF, in the absence of a phase transition. Our simulations of a microscopic model reproduce this dynamics, providing a physical understanding of cooperative adsorption in this industrially important class of materials.

Linker Expansion and Its Impact on Switchability in Pillared-Layer MOFs

Linker elongation is an important method to systematically adjust porosity and pore size in isoreticular MOFs. In flexible structures, this approach opens the possibility for the systematic analysis of the building blocks and their contribution to the overall flexible behavior enabling tuning of the framework responsivity toward molecular stimuli. In this work, we report two new compounds isoreticular to the highly flexible pillared layer structure DUT-8(Ni) ([Ni₂(2,6-ndc)₂(dabco)]_n, 2,6-ndc = 2,6-naphthalenedicarboxylate, dabco = 1,4-diazabicylo[2.2.2]octane). Aromatic linker 2,6-ndc was substituted by longer carboxylic linkers, namely, 4,4'-biphenyldicarboxylate (4,4'-bpdc) and 4,4'-stilbenedicarboxylate (4,4'-sdc), while the dabco pillar was retained. The structural response of the new compounds toward the desolvation and adsorption of various fluids was studied using advanced in situ PXRD techniques, demonstrating distinct differences in the flexible behavior of three compounds and disclosing the impact of linker structure on the framework response. Theoretical calculations provide mechanistic insights and an energetic rationale for the pronounced differences in switchability observed. The energetics of linker bending and linker-linker dispersion interactions govern the phase transitions in investigated MOFs.

Microporous framework membranes for precise molecule/ion separations

Microporous framework membranes such as metal-organic framework (MOF) membranes and covalent organic framework (COF) membranes are constructed by the controlled growth of small building blocks with large porosity and permanent well-defined micropore structures, which can overcome the ubiquitous tradeoff between membrane permeability and selectivity; they hold great promise for the enormous challenging separations in energy and environment fields. Therefore, microporous framework membranes are endowed with great expectations as next-generation membranes, and have evolved into a booming research field. Numerous novel membrane materials, versatile manipulation strategies of membrane structures, and fascinating applications have erupted in the last five years. First, this review summarizes and categorizes the microporous framework membranes with pore sizes lower than 2 nm based on their chemistry: inorganic microporous framework membranes, organic-inorganic microporous framework membranes, and organic microporous framework membranes, where the chemistry, fabrications, and differences among these membranes have been highlighted. Special attention is paid to the membrane structures and their corresponding modifications, including pore architecture, intercrystalline grain boundary, as well as their diverse control strategies. Then, the separation mechanisms of membranes are covered, such as diffusion-selectivity separation, adsorption-selectivity separation, and synergetic adsorption-diffusion-selectivity separation. Meanwhile, intricate membrane design to realize synergistic separation and some emerging mechanisms are highlighted. Finally, the applications of microporous framework membranes for precise gas separation, liquid molecule separation, and ion sieving are summarized. The remaining challenges and future perspectives in this field are discussed. This timely review may provide genuine guidance on the manipulation of membrane structures and inspire creative designs of novel membranes, promoting the sustainable development and steadily increasing prosperity of this field.

Reversible Switching between Nonporous and Porous Phases of a New SIFSIX Coordination Network Induced by a Flexible Linker Ligand

Closed-to-open structural transformations in flexible coordination networks are of potential utility in gas storage and separation. Herein, we report the first example of a flexible SiF₆^2--pillared square grid material, [Cu(SiF₆)(L)₂]_n (L = 1,4-bis(1-imidazolyl)benzene), SIFSIX-23-Cu. SIFSIX-23-Cu exhibits reversible switching between nonporous (β1) and several porous (α, γ1, γ2, and γ3) phases triggered by exposure to N₂, CO₂, or H₂O. In addition, heating β1 to 433 K resulted in irreversible transformation to a closed polymorph, β2. Single-crystal X-ray diffraction studies revealed that the phase transformations are enabled by rotation and geometrical contortion of L. Density functional theory calculations indicated that L exhibits a low barrier to rotation (as low as 8 kJmol^-1) and a rather flat energy surface. In situ neutron powder diffraction studies provided further insight into these sorbate-induced phase changes. SIFSIX-23-Cu combines stability in water for over a year, high CO₂ uptake (ca. 216 cm³/g at 195 K), and good thermal stability.

Smart Molecular Recognition: From Key-to-Lock Principle to Memory-Based Selectivity

The formation and decomposition of inclusion compounds with a solid-solid phase transition may be very selective to the guest molecular structure. This selectivity may function in essentially different ways than defined by the classical concept of molecular recognition, which implies the preferential binding of complementary molecules. Solid inclusion compounds may take part as an initial or/and final state in several processes of different types summarized in this review, which selectivity is boosted by cooperativity of participating molecular crystals. Some of these processes resemble switching electronic devices and can be called smart giving practically absolute molecular recognition.

An N,N'-diethylformamide solvent-induced conversion cascade within a metal-organic framework single crystal

Crystals of a two-dimensional (2D) metal-organic framework (MOF) [Cd3(BTB)2(DEF)4]·2(DEF)0.5 (1; BTB = benzene-1,3,5-tribenzolate; DEF = N,N'-diethylformamide) immersed in a solution of trans-1,2-bis(4-pyridyl)ethylene (BPEE) yields an interpenetrated three-dimensional (3D) MOF of [Cd3(BTB)2(BPEE)(H2O)2]·(BPEE)·xSol (2). Crystals of MOF 2, in turn, undergo a cascade conversion when immersed in DEF, yielding [Cd3(BTB)2(BPEE)1.8(DEF)0.9(H2O)0.8]·xSol (3a) over 100 seconds and [Cd3(BTB)2(BPEE)2(DEF)2]·xSol (4) after one hour, before finally shuttling back to MOF 1 after six hours.

CO2-induced single-crystal to single-crystal transformations of an interpenetrated flexible MOF explained by in situ crystallographic analysis and molecular modeling

A molecular-level investigation is reported on breathing behaviour of a metal-organic framework (1) in response to CO2 gas pressure. High-pressure gas adsorption shows a pronounced step corresponding to a gate-opening phase transformation from a closed (1cp ) to a large-pore (1lp ) form. A plateau is observed upon desorption corresponding to narrow-pore intermediate form 1np which does not occur during adsorption. These events are corroborated by pressure-gradient differential scanning calorimetry and in situ single-crystal X-ray diffraction analysis under controlled CO2 gas pressure. Complete crystallographic characterisation facilitated a rationalisation of each phase transformation in the series 1cp → 1lp → 1np → 1cp during adsorption and subsequent desorption. Metropolis grand-canonical Monte Carlo simulations and DFT-PBE-D3 interaction energy calculations strongly underpin this first detailed structural investigation of an intermediate phase encountered upon desorption.

Tuning the Gate-Opening Pressure in a Switching pcu Coordination Network, X-pcu-5-Zn, by Pillar-Ligand Substitution

Coordination networks that reversibly switch between closed and open phases are of topical interest since their stepped isotherms can offer higher working capacities for gas-storage applications than the related rigid porous coordination networks. To be of practical utility, the pressures at which switching occurs, the gate-opening and gate-closing pressures, must lie between the storage and delivery pressures. Here we study the effect of linker substitution to fine-tune gate-opening and gate-closing pressure. Specifically, three variants of a previously reported pcu-topology MOF, X-pcu-5-Zn, have been prepared: X-pcu-6-Zn, 6=1,2-bis(4-pyridyl)ethane (bpe), X-pcu-7-Zn, 7=1,2-bis(4-pyridyl)acetylene (bpa), and X-pcu-8-Zn, 8=4,4'-azopyridine (apy). Each exhibited switching isotherms but at different gate-opening pressures. The N₂ , CO₂ , C₂ H₂ , and C₂ H₄ adsorption isotherms consistently indicated that the most flexible dipyridyl organic linker, 6, afforded lower gate-opening and gate-closing pressures. This simple design principle enables a rational control of the switching behavior in adsorbent materials.

Regeneration, degradation, and toxicity effect of MOFs: Opportunities and challenges

Metal organic frameworks (MOFs) have been investigated extensively for separation, storage, catalysis, and sensing applications. Nonetheless, problems associated with their toxicity, recycling/reuse/regeneration, and degradation have yet to be addressed as one criterion to satisfy their commercialization. Here, the challenges associated with MOF-based technology have been explored to further expand their practical utility in various applications. We start a brief description of challenges associated with MOF-based technology followed by a critical evaluation of toxicity and need of technical options for regeneration of MOFs. Importantly, diverse techniques/process for reuse and regeneration of MOFs like activation of MOFs by heat, vacuum, solvent exchange, supercritical carbon dioxide (SCCO₂) and other miscellaneous options have been discussed with recent examples. Afterward, we also present an economical aspect and future perspectives of MOFs for real world applications. All in all, we aimed to present opportunities and critical review of the current status of MOF technology with respect to their recycling/reuse/regeneration to consider their environmental impact.

Surface nano-engineered wheat straw for portable and adjustable water purification

Wheat straw (WS), as a cheap and abundant agricultural waste, is usually burned directly in farmland and causes severe air pollution. Therefore, biochar derived from waste WS is prepared and modified by nanoscaled zinc oxide through a facile in-situ surface-modification process. For ease of use, a 3D printed finger-sized unit (FSU) loaded with the above as-prepared WS is designed and implemented. Each unit weighs only 4 g, and could simultaneously reduce three major water contaminants: bacteria, organic dyes, and heavy metal ions. Moreover, it is interesting to note that fresh wheat straw is a flexible material and has excellent electrical conductivity after carbonization. These two properties (flexibility and conductivity) could further adjust water purification performance. The subsequent cellular and animal tests confirmed the biosafety of the water purified with FSU alone.

A new dynamic framework with direct in situ visualisation of breathing under CO2 gas pressure

Structural evidence from in situ single-crystal X-ray diffraction analysis reveals flexibility in a new non-interpenetrated pillared-layer MOF that switches between a wide-pore and a narrow-pore form.

Coordination Network That Reversibly Switches between Two Nonporous Polymorphs and a High Surface Area Porous Phase

We report a 2-fold interpenetrated primitive cubic (pcu) network X-pcu-5-Zn, [Zn₂(DMTDC)₂(dpe)] (H₂DMTDC = 3,4-dimethylthieno[2,3- b]thiophene-2,5-dicarboxylic acid, dpe = 1,2-di(4-pyridyl)ethylene), that exhibits reversible switching between an as-synthesized "open" phase, X-pcu-5-Zn-α, and two nonporous or "closed" polymorphs, X-pcu-5-Zn-β and X-pcu-5-Zn-γ. There are two unusual features of X-pcu-5-Zn. The first relates to its sorption properties, which reveal that the α form exhibits high CO₂ uptake (ca. 255 cm³/g at 195 K) via reversible closed-to-open switching (type F-IV isotherm) of the type desirable for gas and vapor storage; there are only three other reports of porous materials that combine these two features. Second, we could only isolate the β form by activation of the CO₂ loaded α form and it persists through multiple CO₂ adsorption/desorption cycles. We are unaware of a new polymorph having been isolated in such a manner. That the observed phase changes of X-pcu-5-Zn-α occur in single-crystal-to-single-crystal fashion enabled structural characterization of the three forms; γ is a coordination isomer of α and β, both of which are based upon "paddlewheel" clusters.

Visualizing Structural Transformation and Guest Binding in a Flexible Metal-Organic Framework under High Pressure and Room Temperature

Understanding the effect of gas molecules on the framework structures upon gas sorption in porous materials is highly desirable for the development of gas storage and separation technologies. However, this remains challenging for flexible metal-organic frameworks (MOFs) which feature "gate-opening/gate-closing" or "breathing" sorption behaviors under external stimuli. Herein, we report such a flexible Cd-MOF that exhibits "gating effect" upon CO₂ sorption. The ability of the desolvated flexible Cd-MOF to retain crystal singularity under high pressure enables the direct visualization of the reversible closed-/open-pore states before and after the structural transformation as induced by CO₂ adsorption/desorption through in situ single-crystal X-ray diffraction experiments. The binding sites of CO₂ molecules within the flexible MOF under high pressure and room temperature have also been identified via combined in situ single-crystal X-ray diffraction and powder X-ray diffraction studies, facilitating the elucidation of the states observed during gate-opening/gate-closing behaviors. Our work therefore lays a foundation to understand the high-pressure gas sorption within flexible MOFs at ambient temperature, which will help to improve the design efforts of new flexible MOFs for applications in responsive gas sorption and separation.

Insight Studies on Metal-Organic Framework Nanofibrous Membrane Adsorption and Activation for Heavy Metal Ions Removal from Aqueous Solution

Electrospun nanofiber composite membranes containing water-stable metal-organic frameworks (MOFs) particles (Zr-based MOF-808) supported on polyacrylonitrile (PAN) nanofiber synthesized via co-electrospinning have been prepared. MOF particles were dispersed in the organic polymer, and their subsequent presence was inferred by scanning electron microscopy. Membrane performance in heavy metal ion adsorption in batch filtration was evaluated on the basis of Cd²⁺ and Zn²⁺ ions sequestration. The adsorption capacities of the pristine MOF and the MOF composite membrane revealed that MOF particles in the membrane could be accessed for adsorption in the hydrophilic PAN membranes. The maximum adsorption capacities were 225.05 and 287.06 mg g^-1 for Cd²⁺ and Zn²⁺, respectively. Conventional thermal activation of pristine MOF and composite membrane revealed a crystal downsizing, while "hydractivation" produced an expanded MOF with enhanced adsorption potentials. The PAN/MOF-808 "hydractivated" composite membrane could treat 580 mL of Cd, whereas the conventional vacuum-activated composite treated 464 mL. The high separation performance and reusability of the membranes and the outstanding water stability of the MOFs suggested the developed membrane as a potential candidate for water treatment.

Breathing Europium-Terbium Co-doped Luminescent MOF as a Broad-Range Ratiometric Thermometer with a Contrasting Temperature-Intensity Relationship

Solvothermal reactions of lanthanide salts and a semirigid tripodal H₃tatab (4,4',4″-s-triazine-1,3,5-triyltri-p-aminobenzoic acid) ligand in mixed water and N-methyl pyrrolidone (NMP) generated novel breathing MOFs [Ln(tatab)]·solvent (Ln = Eu in 1-Eu, Tb in 1-Tb, Eu_0.015Tb_0.985 in 1-Eu_0.015Tb_0.985). The framework of 1 was contracted upon removal of guests to form partly desolvated [Ln (tatab)]·3.7H₂O·2.5NMP (1'). Single-crystal X-ray analyses demonstrated that 1 has the breathing ability to spontaneously release guests and maintain the same topology. In contrast to as-synthesized 1, the cell volume of 1' decreased markedly upon removal of the guests. Different from linear dicarboxylates, the semirigid tripodal tatab ligand is bridged to an inorganic Ln-O chain, limiting the rotation around the O-O-axis of carboxylate. The breathing mechanism is based on the flexible C-N-C angles of amide bonds in the tatab ligand, causing a change in the solvent-accessible volume in the framework. Interestingly, the luminescence color of breathing co-doped lanthanide MOF 1'-Eu_0.015Tb_0.985 is blue-shifted and turned from orange to green with an increase in temperature, which can be attributed to a change in the relative intensity of Tb and Eu emissions, and is quite different from that observed for the reported related compounds. The breathing co-doped lanthanide MOF 1'-Eu_0.015Tb_0.985 can be applied as a high-sensitivity ratiometric thermometer in a broad temperature from 90 to 300 K.

Readily accessible shape-memory effect in a porous interpenetrated coordination network

Shape-memory effects are quite well-studied in general, but there is only one reported example in the context of porous materials. We report the second example of a porous coordination network that exhibits a sorbate-induced shape-memory effect and the first in which multiple sorbates, N₂, CO₂ and CO promote this effect. The material, a new threefold interpenetrated pcu network, [Zn₂(4,4'-biphenyldicarboxylate)₂(1,4-bis(4-pyridyl)benzene)]_n (X-pcu-3-Zn-3i), exhibits three distinct phases: the as-synthesized α phase; a denser-activated β phase; and a shape-memory γ phase, which is intermediate in density between the α and β phases. The γ phase is kinetically stable over multiple adsorption/desorption cycles and only reverts to the β phase when heated at >400 K under vacuum. The α phase can be regenerated by soaking the γ phase in N,N'-dimethylformamide. Single-crystal x-ray crystallography studies of all three phases provide insight into the shape-memory phenomenon by revealing the nature of interactions between interpenetrated networks. The β and γ phases were further investigated by in situ coincidence powder x-ray diffraction, and their sorption isotherms were replicated by density functional theory calculations. Analysis of the structural information concerning the three phases of X-pcu-3-Zn-3i enabled us to understand structure-function relationships and propose crystal engineering principles for the design of more examples of shape-memory porous materials.

Recyclable switching between nonporous and porous phases of a square lattice (sql) topology coordination network

A 2D switching material holds great potential for exceptional working capacity of gas storage.

Two lanthanide metal–organic frameworks as sensitive luminescent sensors for the detection of Cr2+ and Cr2O72− in aqueous solutions

Two lanthanide–organic frameworks [Ln(HPIDC)(m-bdc)·1.5H₂O]_n (Ln = Eu 1 or Tb 2; H₃PIDC = 2-(4-pyridyl)-1H-imidazole-4,5-dicarboxylic acid; m-H₂bdc = 1,3-benzenedicarboxylic acid) were synthesized under hydrothermal conditions.

Exploring the reversible host–guest chemistry of a crystalline octanuclear Ag(i) metallosupramolecular macrocycle formed from a simple pyrazinylpyridine ligand

High nuclearity Ag(i) assemblies are prepared from simple polytopic ligands, including an octanuclear metallomacrocycle which exhibits reversible and selective guest exchange.

Gate-opening upon CO2 adsorption on a metal–organic framework that mimics a natural stimuli-response system

A dynamic d-champhorate-based protuberant-grid-type framework, undergoes gate opening and closing processes that were triggered by the stimuli of the adsorption or desorption of CO₂. It is able to specifically recognize CO₂ over than N₂ and H₂ and shows a high CO₂ uptake of 90 mg g⁻¹ under 35 bar at 298 K.

NIR emission and luminescent sensing of a lanthanide–organic framework with Lewis basic imidazole and pyridyl sites

Three luminescent lanthanide–organic frameworks, [Ln(Himdc)(ina)(H₂O)]_n, consist of a 3D microporous lanthanide carboxylate ([Eu(COO)₃]_n) framework and imidazole and pyridyl sites for the luminescent sensor.