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Several approaches have recently been investigated with the aim of enhancing the specific capacitance of polyaniline (PANI). We herein report a novel pathway to boost the specific capacitance of PANI, which is highly tunable and versatile, based on wet chemistry techniques. In this approach, utilization of a specific metal-organic framework (MOF), UiO-66-NH2, as a nanopore generator (Nanogen) is demonstrated. This systematic study demonstrates a tight interplay between the enhanced electrolyte accessibility to the PANI chains, through the incorporation of MOF nanogens, and the optimal relative amount of the conductive PANI, necessary to attain a charge percolation threshold in the binary system (MOF@PANI). Satisfying the charge percolation while maintaining porosity is necessary to arrive at a maximized specific capacitance of the PANI as the active phase. The enhancement in the specific capacitance of the PANI was fully exploited through a systematic investigation that helped to pinpoint the saddle point at which the two orthogonal properties, namely porosity (electrolyte diffusivity) and charge mobility (PANI inter-chain electronic conductivity) can be fine-tuned via controlling the materials composition. Of the different compositions investigated, the composite containing 23 wt% PANI of the total weight, doped with MOF nanogens, resulted in an enhanced specific capacitance of 872 F g-1 for the PANI, in comparison to only 469 F g-1 for the pristine PANI investigated under identical conditions.

Adenosine is a small molecule directly involved in maintaining homeostasis under pathological and stressful conditions. Due to its rapid metabolism, delivery vehicles capable of exhibiting extended release of adenosine are of paramount interest. Herein, we demonstrate a superior long-term (9 days) release profile of adenosine from biocompatible MOFs in a physiologically relevant environment. The key to the biocompatibility of MOFs is their stability under biologically relevant conditions. This study additionally highlights the interplay between the chemical stability of prototypal MOFs, assessed under physiological conditions, and their cytotoxicity profiles. Cytotoxicity of the prototypal Zn-based MOF (ZIF-8) and three Zr-based MOFs (UiO-66, UiO-66-NH

Current interest in investigating non-precious group (NPG) metals for catalyzing the oxygen evolution reaction (OER) has revealed that doping of Ni hydroxides with Fe results in the dramatic enhancement of catalytic activity. Herein, a facile pathway to construct tetrataenite, an NiFe alloy of extraterrestrial origin and to address the limited electrical conductivity of metal oxides/hydroxides by directly constructing them atop graphene sheets is described. In this approach, a one-pot, bottom-up assembly of hybrid ultramicroporous materials (HUMs) was carried out, in the presence of suspended graphene (G), to homogeneously deposit the HUMs on unmodified graphene sheets, affording HUMs@G. Single metal (SIFSIX-3-Ni@G) and mixed metal (SIFSIX-3-NiFe@G) HUMs can be readily synthesized from their respective metal salts to afford a well-designed catalyst for the OER. The pyrolysis of SIFSIX-3-NiFe@G resulted in the deposition of the nanoalloy tetrataenite on G, demonstrating an exceptionally low OER onset potential of 1.44 V vs. RHE and reduced overpotential at 10 mA cm-2 (η10 = 266 mV). The synergy between the composition of the active catalyst and the electronically conductive support was attained by designing a reaction system encoding the self-assembly of a crystalline pre-catalyst on G sheets.

The remarkable water stability of Zr-carboxylatebased metal-organic frameworks (MOFs) stimulated considerable interest toward their utilization in aqueous phase applications. The origin of such stability is probed here through pH titration and plc modeling. A unique feature of the Zr-6(mu 3OH)(4)(mu O-3)(4)(RCO2)(12) cluster is the Zr-bridging oxo/hydroxyl groups, demonstrating several pK(a) values that appear to provide for the water stability at a wide range of pH. Accordingly, the tunability of the cage/surface charge of the MOF can feasibly be controlled through careful adjustment of solution pH. Such high stability, and facile control over cage/surface charge, can additionally be augmented through introducing chemical functionalities lining the cages of the MOF, specifically amine groups in the UiO-66-NH2 presented herein. The variable protonation states of the Zr cluster and the pendant amino groups, their H-bond donor/acceptor characteristics, and their electrostatic interactions with guest molecules were effectively utilized in controlled experiments to demonstrate high uptake of model guest molecules (137 mg/g for Cr(VI), 1275 mg/g for methylene blue, and 909 mg/g for methyl orange). Additionally, a practical form of the silica-supported MOF, UiO-66-NH2 @SiO2, constructed in under 2 h reaction time, is described, generating a true platform microporous sorbent for practical use in demanding applications.

We present a novel approach to produce a composite of the HKUST-1 metal-organic framework (MOF) and graphene, which is suited for the fabrication of monolithic coatings of solid substrates. In order to avoid the degradation of graphene electrical properties resulting from chemical functionalization (e.g., oxidation yielding graphene oxide, GO), commercial, nonmodified graphene was utilized. The one-pot synthesis of the moldable composite material allows for a controllable loading of graphene and the tuning of porosity. Potentially, this facile synthesis can be transferred to other MOF systems. The monolithic coatings reported here exhibit high surface areas (1156-1078 m

A comprehensive model to describe the water stability of prototypical metal–organic frameworks (MOFs) is derived by combining different types of theoretical and experimental approaches. The results provide an insight into the early stages of water-triggered destabilization of MOFs and allow detailed pathways to be proposed for the degradation of different MOFs under aqueous conditions. The essential elements of the approach are computing the pKa values of coordinated water molecules and geometry relaxations. Variable-temperature and pH infrared spectroscopy techniques are used to corroborate the main findings. The model developed herein helps to explain stability limits observed for several prototypical MOFs, including MOF-5, HKUST-1, UiO-66, and MIL-101-Cr, in aqueous solutions, and thus, provides an insight into the possible degradation pathways in acidic and basic environments. The formation of a metal hydroxide through the autoprotolysis of metal-coordinated water molecules and the strength of carboxylate–metal interactions are suggested to be two key players that govern stability in basic and acidic media, respectively. The methodology presented herein can effectively guide future efforts, which are especially significant for in silico screening, for developing novel MOFs with enhanced aqueous stability.

A one-pot synthesis in quantitative yield is described to construct a composite of the amino-derivative Zr carboxylate metal–organic framework (MOF) and silica gel (UiO-66-NH2@silica). The silica gel was utilized as a porous solid support to enable enhanced column packing efficiency and increase the sorbent–solute contact time. The control experiment conducted on bare silica unambiguously established the active role of the amino-functionalized MOF as the ion-exchange element in the novel composite. The column prepared from this composite shows excellent hexavalent chromium uptake (Cr2O72− uptake of 277.4 mg g−1). Remarkably, this ion exchange column is capable of eliminating Cr(VI) ions even in the presence of competing anions including chloride, bromide, nitrate and sulphate, thus indicating its potential for applications in municipal as well as industrial waste water treatment.

A facile one-pot, bottom-up approach to construct composite materials of graphene and a pyrimidine-based porous-organic polymer (PyPOP), as host for immobilizing human hemoglobin (Hb) biofunctional molecules, is reported. The graphene was selected because of its excellent electrical conductivity, while the PyPOP was utilized because of its pronounced permanent microporosity and chemical functionality. This approach enabled enclathration of the hemoglobin within the microporous composite through a ship-in-a-bottle process, where the composite of the PyPOP@G was constructed from its molecular precursors, under mild reaction conditions. The composite-enclathrated Fe-protoporphyrin-IX demonstrated electrocatalytic activity toward oxygen reduction, as a functional metallocomplex, yet with a distinct microenvironment provided by the globin protein. This approach delineates a pathway for platform microporous functional solids, where fine-tuning of functionality is facilitated by judicious choice of the active host molecules or complexes, targeting specific application.

A porous-organic polymer (POP) was constructed through bottom-up assembly from its molecular precursors atop multi-walled carbon nanotubes (MWCNTs) in a one-pot synthesis, affording a composite material POP@MWCNTs. The composite was found to be microporous and with pronounced affinity towards gaseous CO 2 (heat of adsorption of ∼45 kJ/mol at initial coverage). The composite was characterized through several techniques including gas sorption, FTIR spectroscopy, SEM, AFM, and TEM microscopy, elemental analysis and thermogravimetric (TGA) analyses. The homogenous coating of the POP on top of the MWCNTs was evident from its electron microscopy images. Quantum mechanical calculations for geometry optimization of a fragment of the polymer and of the composite indicated rigidified structure of the POP in contact with the MWCNTs, further supporting and explaining the findings from the gas sorption measurements conducted herein. In Addition, the composite was found to be electrochemically active towards CO 2 reduction, surpassing the properties of either of its two components, indicating enhanced interfacial interactions between the MWCNTs and the POP. Moreover, the catalytic behavior of the composite was straightforwardly enhanced through post-synthetic incipient wetness impregnation of Cu(I) ions, demonstrating tunnability of the catalyst. This approach delineates a pathway to merge the properties of both families of materials, on the molecular level, aiming to extend the realms of microporous solids into electrocatalytic CO 2 capture and sequestration technologies.

The remarkable water stability of Zr-carboxylate-based metal-organic frameworks (MOFs) stimulated considerable interest toward their utilization in aqueous phase applications. The origin of such stability is probed here through pH titration and p

A number of permanently porous polymers containing Ru(bpy)n photosensitizer or a cobaloxime complex, as a proton-reduction catalyst, were constructed via one-pot Sonogashira-Hagihara (SH) cross-coupling reactions. This process required minimal workup to access porous platforms with control over the apparent surface area, pore volume, and chemical functionality from suitable molecular building blocks (MBBs) containing the Ru or Co complexes, as rigid and multitopic nodes. The cobaloxime molecular building block, generated through in situ metalation, afforded a microporous solid that demonstrated noticeable catalytic activity toward hydrogen-evolution reaction (HER) with remarkable recyclability. We further demonstrated, in two cases, the ability to affect the excited-state lifetime of the covalently immobilized Ru(bpy)3 complex attained through deliberate utilization of the organic linkers of variable dimensions. Overall, this approach facilitates construction of tunable porous solids, with hybrid composition and pronounced chemical and physical stability, based on the well-known Ru(bpy)nor the cobaloxime complexes.

We report on a one-pot synthesis of Zr–carboxylate porous polymers. This approach utilized the orthogonality between carboxylate–Zr coordination and C–C cross coupling reactions. The multitopic carboxylate linkers necessary to extend the connectivity of Zr–carboxylate precursors were constructed, in situ, through Sonogashira–Hagihara cross coupling from their molecular precursors. Several halogenated aromatic precursors including the pyridine and pyrimidine derivatives were utilized due to their desirable binding energetics to CO2. The obtained compounds demonstrated permanent porosity as determined by their gas sorption analyses. Several characterization techniques including FTIR, SEM, EDX and solid-state NMR spectroscopy, were utilized to help constructing structure–function relationships. Additionally, impact of chemical composition, specifically incorporation of basic binding sites, on the CO2 affinity to the reported polymers is outlined. The reported isosteric heat of adsorption (37–42 kJ mol−1) for the pyridine and pyrimidine-based solids are among the highest reported for Zr-based MOFs.

A one-pot, bottom-up assembly of a pyrimidine-containing porous-organic polymer (PyPOP) was conducted to homogenously deposit the PyPOP atop unmodified graphene sheets, affording a composite material PyPOP@G. The PyPOP demonstrated an appreciable affinity toward CO2 capture but was found to be largely insulating, hindering its usage in potential electrochemical conversion of CO2. However, its composite with graphene was found to be microporous, with maintained affinity toward CO2 and furthermore demonstrated significant electrochemical activity toward CO2 reduction (5 mA cm−2 at −1.6 V), not observed in either of its two components separately.

Herein, we outline a facile and promising approach in which microporous organic polymer matrices were constructed from their molecular building blocks, in the presence of surface-functionalized Au nanoparticles (AuNPs) as one component of the system. This approach permitted the construction of microporous networks around AuNPs and consequently allowed controlling access of small guest molecules to the surface of the AuNPs. Gas sorption measurements confirmed the permanent microporosity of the composites, and furthermore demonstrated interdependence between the size and degree of connectivity of the molecular linkers, the amount of AuNPs added to the initial reaction mixture, and porosity of the composites. A clear electrocatalytic activity dependence on the molecular size of the substrate and pore system of the host matrix is demonstrated. Of special significance is the enhanced catalytic activity of the investigated composites towards borohydride oxidation (mass activity of 8.8–12 mA mg−1) as compared to flat Au electrode (1.6 mA mg−1). These results show a versatile pathway to utilize decorated AuNPs, as functionalized building units, in construction of porous solids with hybrid composition and tunable properties.

Synthesis of conformal coatings of MOFs, especially water stable ones, on different surfaces is of paramount interest due to their potential applications including electrocatalysis, sensing, and separation. Despite previous efforts that resulted in successful deposition of thin-films of MOFs on flat surfaces, a rapid, low cost, and atom-efficient synthesis of such thin-films is still challenging. Herein we report a flash synthesis to produce conformal coatings of the water-stable UiO-66-NH2 on different flat or patterned surfaces, including Si and Au-coated Si wafers, glass slides, TLC silica plates, carbon-coated and FTO-coated electrodes. The flash synthesis presented herein is accomplished within ten minutes reaction time, utilizing minimal amounts of solvent and reagents, and thus is a greener synthesis to attain conformal coatings of such MOF on solid surfaces. The versatility of the approach is demonstrated by successful conformal coatings of the UiO-66-NH2 on Si, Au, glass, silica, as well as carbon surfaces, all achieved through drop-casting on the respective substrate at 100 °C for 10 min. The utility of such thin layer coating of microporous solids in supercapacitor applications, thin layer chromatography, as well as detection of heavy metal ions in aqueous solutions is also demonstrated.

Modulating the conductivity of microporous metal-organic frameworks (MOFs) through formulation of composites with graphene (G), as the conductive element, is demonstrated, without being limited to a particular MOF composition or topology. The synthesis allows for varying G content within the composite systematically, resulting in highly electrically conductive composites beyond 30 wt% G. The charge percolation model can effectively be utilized to describe the macroscopic electrical conductivity of the synthesized composites. Starting from a non-conductive MOF (HKUST-1, σ = 2*10−8 S m−1), enhanced conductivity can be accessed through increasing the G wt%, reaching more than nine orders of magnitude increase in conductivity up to 23.3 S m−1 for the composite containing 59.4 wt% G. A charge percolation threshold of 30 wt% G was observed, where sufficient G-G contacts were established within the composite. The ab initio DFT calculations on Cu-paddlewheel@G model indicated several non-covalent interactions, including OH⋯π and π‒π interactions, governing the deposition of the MOF on top of G (range of ‒101.3 kJ/mol to −113.8 kJ/mol). This approach is potentially transferable to the vast majority of MOFs, as surface functionalization of the conductive filler is not a prerequisite for the attainment of bottom-up assembly of the MOF@G.

Herein, we report a facile approach towards the construction of poly-functional porous organic polymers (POPs). The functional groups employed were selected to span the range of Lewis-base to neutral to Lewis-acid character. Our results underline the effect of chemical functionality on the observed Qst for CO2 adsorption inside the material, being largest for functional groups with electron donating O- and N-centered Lewis base sites. Our systematic investigation within a family of POPs revealed a wide range for CO2 heat of adsorption (23.8–53.8 kJ mol−1) that is clearly associated with the chemical nature of the functional groups present. In addition, post-synthetic modification of POPs reported herein demonstrated a facile pathway to dramatically enhance carbon dioxide uptake energetics.

peer-reviewed Representative compounds from three classes of microporous solids, namely metal-organic frameworks (MOFs), hybrid ultramicroporous materials (HUMs) and porous-organic polymers (POPs), were investigated for their nitric oxide gas uptake and release behavior. Low pressure sorption studies indicated strong chemisorption of NO on the free amine groups decorating the MOF UiO-66-NH2 when compared to its non-amine functionalized parent. The HUMs demonstrated reversible physisorption within the low pressure regime but interestingly in one case there was evidence for chemisorption following pressurization with NO at 10 bar. Significant release of chemisorbed NO from the UiO-66-NH2 and one of the HUMs was triggered by addition of acid to the medium, a pH change from 7.4 to 5.4 being sufficient to trigger NO release. An imidazole-based POP exhibited chemisorption of NO at high pressure wherein the ring basicity facilitated both NO uptake and spontaneous release upon contact with the aqueous release medium.

A one-pot, bottom-up assembly of a pyrimidine-containing porous-organic polymer (PyPOP) was conducted to homogenously deposit the PyPOP atop unmodified graphene sheets, affording a composite material PyPOP@G. The PyPOP demonstrated an appreciable affinity toward CO