Zr6 Clusters Research Articles

Building Block Symmetry Relegation Induces Mesopore and Abundant Open-Metal Sites in Metal–Organic Frameworks for Cancer Therapy

Building Block Symmetry Relegation Induces Mesopore and Abundant Open-Metal Sites in Metal–Organic Frameworks for Cancer Therapy

Porphyrin-Based Metal-Organic Frameworks for Efficient Photocatalytic H2 Production under Visible-Light Irradiation.

Metal-organic frameworks (MOFs) are important photocatalytic materials for H2 production. To clarify the structure-function relationship and improve the photocatalytic activity, herein we explored a series of porphyrin-based zirconium MOFs (PCN-H2/Ptx:y, where x:y = 4:1, 3:2, 2:3, and 0:1) containing different ratios of H2TCPP and PtIITCPP [TCPP = tetrakis(4-carboxyphenyl)porphyrinate] as isostructural ligands and Zr6 clusters as nodes. Under visible-light irradiation, PCN-H2/Pt0:1 shows the highest average H2 evolution reaction rate (351.08 μmol h-1 g-1), which decreases along with lowering of the ratio of PtIITCPP in the PCN-H2/Ptx:y series. The differences in photocatalytic activity are attributed to more uniformly dispersed Pt2+ ions in PCN-H2/Pt0:1, which promotes charge transfer from porphyrins (photosensitizers) to PtII ions (catalytic centers), leading to efficient charge separation in the MOF materials. The bifunctional MOFs with photosensitizers and catalytic centers provide new insight for the design and application of porphyrin-based photocatalytic systems for visible-light-driven H2 production.

Boosted peroxidase-like activity of metal-organic framework nanoparticles with single atom Fe(Ⅲ) sites at low substrate concentration

Single atom nanomaterials possess catalytic activity like natural enzymes are termed as SAzymes which have gained great attention during last two years because of the maximal utilization of atoms and the benefit of understanding structure-property relationship. However, most of SAzymes are fabricated based on hydrophobic carbon, which disperse poorly in water and exhibit inferior affinity towards substrates, which may limit their biomedical applications. Here, we report a peroxidase-like SAzyme through the post-modification route based on hydrophilic defective metal-organic frameworks. Hydrochloric acid (HCl) is employed as ligand modulator to fabricate defective NH2-UiO-66 nanoparticles (HCl–NH2-UiO-66 NPs). Compared with the NPs fabricated through acetic acid modulation method (Ac-NH2-UiO-66 NPs), HCl–NH2-UiO-66 NPs have more missing linkers. Hence, more Fe(Ⅲ) ions can be successfully doped onto Zr6 clusters in HCl–NH2-UiO-66 NPs in a single atom state via formation of Fe–O–Zr bridge. The HCl–NH2-UiO-66 NPs doped with Fe(Ⅲ) ions (Fe–HCl–NH2-UiO-66 NPs) possess higher peroxidase-like activity than Fe-Ac-NH2-UiO-66 NPs due to the higher loading amount of Fe. Besides, both Fe–HCl–NH2-UiO-66 NPs and Fe-Ac-NH2-UiO-66 NPs exhibit lower Michaelis-Menten constants (Km) for hydrogen peroxide (H2O2) than most reported nanomaterials, indicating their higher affinity to H2O2. Due to their excellent catalytic activity to low concentration of substrates, Fe–HCl–NH2-UiO-66 NPs can detect H2O2 with a limit of detection (LOD) of 1.0 μM. Thus, our system can be used to detect the low cellular H2O2 concentration. With high peroxidase-like activity induced by plenty of single atom Fe(Ⅲ) sites, Fe–HCl–NH2-UiO-66 NPs can also find wide applications in other fields including nanomedicine, pollution degradation and catalysis.

The cascade catalysis of the porphyrinic zirconium metal–organic framework PCN-224-Cu for CO2conversion to alcohols

The Zr6cluster and TCPP-Cu unit in the PCN-224-Cu act like organelles during chemocatalytic CO2conversion to alcohols.

Topological Strain-Induced Regioselective Linker Elimination in a Chiral Zr(IV)-Based Metal-Organic Framework

Summary Zr-carboxylate metal-organic frameworks (MOFs) are structurally robust materials, in part due to their strong coordination bonds. The regioselective Zr–O bond cleavage and formation between 3D architectures are thus challenging and are heretofore unexplored. In this work, by introducing highly flexible 18-crown-6-ether functionalities into a homochiral Zr-MOF, we report an unprecedented topology transition in which a 4,10-connected framework undergoes a rapid solid-state transition into a thermodynamically more stable 4,8-connected analog by a regioselective-linker-elimination under ambient conditions. The transition process was unambiguously unraveled by single-crystal and powder X-ray diffraction studies, and we proposed a possible transition mechanism based on various control experiments and theoretical calculations. The excellent chemical stability and substantially expanded porosity and pore apertures endowed the transformed chiral MOF with an exceptional capacity for the enantioadsorptive and solid-phase extractive separation of the racemic drug molecule of lansoprazole with 98% ee and 93% ee, respectively.

Synthesis, Structural, and Physicochemical Characterization of a Ti6 and a Unique Type of Zr6 Oxo Clusters Bearing an Electron-Rich Unsymmetrical {OON} Catecholate/Oxime Ligand and Exhibiting Metalloaromaticity.

The chelating catechol/oxime ligand 2,3-dihydroxybenzaldehyde oxime (H3dihybo) has been used to synthesize one titanium(IV) and two zirconium(IV) compounds that have been characterized by single-crystal X-ray diffraction and 1H and 13C NMR, solid-state UV-vis, and ESI-MS spectroscopy. The reaction of TiCl4 with H3dihybo and KOH in methanol, at ambient temperature, yielded the hexanuclear titanium(IV) compound K2[TiIV6(μ3-O)2(μ-O)3(OCH3)4(CH3OH)2(μ-Hdihybo)6]·CH3OH (1), while the reaction of ZrCl4 with H3dihybo and either nBu4NOH or KOH also gave the hexanuclear zirconium(IV) compounds 2 and 3, respectively. Compounds 1-3 have the same structural motif [MIV6(μ3-Ο)2(μ-Ο)3] (M = Ti, Zr), which constitutes a unique example with a trigonal-prismatic arrangement of the six zirconium atoms, in marked contrast to the octahedral arrangement of the six zirconium atoms in all the Zr6 clusters reported thus far, and a unique Zr6 core structure. Multinuclear NMR solution measurements in methanol and water proved that the hexanuclear clusters 1 and 3 retain their integrity. The marriage of the catechol moiety with the oxime group in the ligand H3dihybo proved to be quite efficient in substantially reducing the band gaps of TiO2 and ZrO2 to 1.48 and 2.34 eV for the titanium and zirconium compounds 1 and 3, respectively. The application of 1 and 3 in photocurrent responses was investigated. ESI-MS measurements of the clusters 1 and 3 revealed the existence of the hexanuclear metal core and also the initial formation of trinuclear M3 (M = Ti, Zr) building blocks prior to their self-assembly into the hexanuclear M6 (M = Ti, Zr) species. Density functional theory (DFT) calculations of the NICSzz scan curves of these systems revealed that the triangular M3 (M = Ti, Zr) metallic ring cores exhibit pronounced metalloaromaticity. The latter depends upon the nature of the metallic center with NICSzz(1) values equal to -30 and -42 ppm for the Ti (compound 1) and Zr (compound 2) systems, respectively, comparable to the NICSzz(1) value of the benzene ring of -29.7 ppm calculated at the same level of theory.

Functionalization of zirconium-based metal–organic frameworks for gas sensing applications

The functionalization and incorporation of noble metals in metal–organic frameworks have been widely used as efficient methods to enhance their applicability. Herein, a sulfone-functionalized Zr-MOF framework labeled Zr–BPDC–SO2 (BPDC–SO2 =dibenzo[b,d]-thiophene-3,7-dicarboxylate 5,5-dioxide) and its Pd-embedded composite were efficiently synthesized by adjusting their functional groups. The obtained compounds were characterized to assess their potential for gas sensing applications. X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, specific surface area measurements, and thermogravimetric analysis were employed to characterize the new sensor materials. The gas sensing properties of the novel functionalized sensor materials were systematically investigated under various temperature, concentration, and gas type conditions. Owing to the strong hydrogen bonds of the sulfonyl groups and Zr6 clusters in the framework with the hydroxyl groups of ethanol, Zr–BPDC–SO2 emerged as an effective sensor for ethanol detection. In addition, Pd@Zr–BPDC–SO2 exhibited efficient hydrogen sensing performance, in terms of sensor dynamics and response. More importantly, the material showed a higher sensing response to hydrogen than to other gases, highlighting the important role of Pd in the Zr-MOF-based hydrogen sensor. The results of the sensing tests carried out in this study highlight the promising potential of the present materials for practical gas monitoring applications.

Static and Dynamic Adsorptions of Water Vapor by Cyclic [Zr36] Clusters: Implications for Atmospheric Water Capture Using Molecular Solids

A 36‐nuclear Zr(IV) cluster based on six [Zr6O4(OH)4] units is found to form three different crystal structures depending on synthesis conditions. The cubic phase (ZF‐3c) is obtained when the cyclic clusters are interlinked by Na+ or K+ ions. In the absence of alkali metal ions, either tetragonal (ZF‐3t) or hexagonal (ZF‐3h) packing structures are formed. All the solids remain crystalline after evacuation, and ZF‐3h possesses a permanent porosity. Upon repeated adsorptions of water vapor, the three different molecular solids comprising the same building blocks turn amorphous; however, overall uptake properties are not deteriorated and reproducible isotherms are observed featuring fast uptake at low relative humidity and unrestricted uptake at RH > 90%. A good reproducibility has also been established in cyclic adsorption–desorption measured under dynamic flow conditions, and, especially ZF‐3t displays the working capacity 2.7 times that of zeolite 4A thanks to the fast desorption kinetics.

Microwave-Assisted Solvothermal Synthesis of UiO-66-NH2 and Its Catalytic Performance toward the Hydrolysis of a Nerve Agent Simulant

Zr-containing metal-organic frameworks (MOFs) exhibit a good performance of catalyzing the hydrolysis of chemical warfare agents, which is closely related to the size of MOF particles and its defects, but these two factors are often intertwined. In this article, we synthesized UiO-66-NH2 nanoparticles using a microwave-assisted hydrothermal method. By using a new modulator 4-Fluoro-3-Formyl-Benzoic Acid (FFBA) in different proportions, MOF particles with the same defect degree but different scales and those with similar sizes but different defect degrees can be obtained. The performance of the obtained MOF particles to catalyze the hydrolysis of the nerve agent simulant, dimethyl 4-nitrophenyl phosphate (DMNP), was investigated, and the effects of single factors of size or defect were compared for the first time. As the size of the obtained MOF particles increased from 81 nm to 159 nm, the catalytic degradation efficiency toward DMNP gradually decreased, and the half-life increased from 3.9 min to 11.1 min. For MOFs that have similar crystal sizes, the catalytic degradation half-life of MOF3 is only 5 min, which is much smaller than that of MOF5 due to the defects increase from 1.2 to 1.8 per Zr6 cluster.

Extension of Surface Organometallic Chemistry to Metal-Organic Frameworks: Development of a Well-Defined Single Site [(≡Zr-O-)W(═O)(CH2tBu)3] Olefin Metathesis Catalyst.

We report here the first step by step anchoring of a W(≡CtBu)(CH2tBu)3 complex on a highly crystalline and mesoporous MOF, namely Zr-NU-1000, using a Surface Organometallic Chemistry (SOMC) concept and methodology. SOMC allowed us to selectively graft the complex on the Zr6 clusters and characterize the obtained single site material using state of the art experimental methods including extensive solid-state NMR techniques and HAADF-STEM imaging. Further FT-IR spectroscopy revealed the presence of a W═O moiety arising from the in situ reaction of the W≡CtBu functionality with the coordinated water coming from the 8-connected hexanuclear Zr6 clusters. All the steps leading to the final grafted molecular complex have been identified by DFT. The obtained material was tested for gas phase and liquid phase olefin metathesis and exhibited higher catalytic activity than the corresponding catalysts synthesized by different grafting methods. This contribution establishes the importance of applying SOMC to MOF chemistry to get well-defined single site catalyst on MOF inorganic secondary building units, in particular the in situ synthesis of W═O alkyl complexes from their W carbyne analogues.

The metal–organic framework UiO-66 with missing-linker defects: A highly active catalyst for carbon dioxide cycloaddition

Metal-organic frameworks (MOFs) have been confirmed to be a promising material for carbon dioxide capture, while the simultaneous capture and conversion of carbon dioxide over the MOF-based catalysts is furthermore being a hot topic. In this work, we demonstrate that the zirconium-based MOF UiO-66 (UiO for University of Oslo) with missing-linker defects is a highly active catalyst for carbon dioxide cycloaddition with an epoxide, which is a reaction with 100% atom economy and broad industrial uses. A facile, rapid, energy-saving and environmentally friendly argon plasma treatment was employed to create the missing-linker defects in UiO-66 without using hazardous chemicals at atmospheric pressure and temperature below 398 K, whereas the bulk structure of UiO-66 remained stable. The energetic argon plasma species decomposed part of the linkers within UiO-66 structure, leaving unsaturated metal sites. The defect concentration in UiO-66 was tuned by changing the plasma bombardment time. After an argon plasma treatment for 30 min, the number of linker deficiencies per Zr6 cluster can reach up to 2.3. The product yield of the UiO-66 with abundant missing-linker defects increased of ca. 43% over the defect-free UiO-66. The crucial role of the missing-linker defects of UiO-66 in the enhancement of the catalytic activity was confirmed. The present study will be helpful for the future preparation of defective MOFs with potential applications not only for carbon dioxide conversion but also for energy storage and conversion.

Ligand Functionalization in Zirconium‐Based Metal‐Organic Frameworks for Enhanced Carbon Dioxide Fixation

AbstractLigand functionalization has always been considered as an effective method for regulating the catalytic activity of the metal‐organic frameworks (MOFs) materials. Herein, three stable zirconium‐based MOFs (Zr‐MOFs), constructed by the 10‐connected Zr6 cluster and different groups‐decorated V‐shaped ligands (H2L), are successfully synthesized through a facile ligand functionalization method. Subsequently, three isostructural Zr‐MOFs, including the parent structure Zr(H2L), amino‐decorated Zr(H2L) (NH2‐Zr(H2L)), and fluorine and amino bi‐decorated Zr(H2L) (F‐NH2‐Zr(H2L)), are employed as the platform for systematically investigating the effect of Lewis basic groups on the CO2 adsorption and separation behavior, more importantly the CO2 chemical fixation. Benefitting from the decorated Lewis basic groups, not only the CO2 adsorption enthalpy and selectivity over CH4 of NH2‐Zr(H2L) and F‐NH2‐Zr(H2L) are improved, but also their catalytic activities for cycloaddition of CO2 to form cyclic carbonates are significantly enhanced. Among them, F‐NH2‐Zr(H2L) exhibits the most effective performance for cycloaddition of CO2 and styrene epoxide, which can be attributed to the strong polarization between the CO2 molecule and the framework of F‐NH2‐Zr(H2L). Under a mild condition, the yield of F‐NH2‐Zr(H2L) for cycloaddition of CO2 with styrene epoxide can reach up to 97%, which surpasses most of the reported MOFs‐based catalysts.

Adsorption behavior of a metal organic framework of University in Oslo 67 and its application to the extraction of sulfonamides in meat samples

In this work, a dispersive solid phase extraction (d-SPE) method for sulfonamides (SAs) has been developed using a stable and mesoporous metal organic framework (University in Oslo 67, UiO-67) as adsorbent, which was synthesized by coordination of Zr4+ ions with 4, 4-biphenyl-dicarboxylicacid (H2BPDC) through a facile one-pot method. Owing to the synergistic effects of π-π interaction, hydrogen bonding, hydrophobic interaction and size match between SAs and the adsorbent, the extraction performance of UiO-67 for SAs was obviously improved. The adsorption behavior, evaluated by the kinetic models, showed that the intraparticle diffusion was involved during the adsorption process. The proper match between the pore size of UiO-67 (3.49 nm) and the molecular sizes of SAs (1.1 nm × 0.65 nm) not only allowed SAs to diffuse intraparticle but also permitted them to adjust their configurations to form hydrogen bonding with the UiO-67. By combination with HPLC analysis, a simple, sensitive, accurate and precise method for detection of SAs has been established. The method proposed in this work showed good performances, including wide linearity (14.6–250 ng/g) with high correlation coefficients (R ≥ 0.9991), low limits of detection (LODs, 0.7–6.5 ng/g for all SAs), satisfactory precision (Intra-day RSDs ≤ 3.4%, inter-day RSDs ≤ 4.7%), and high accuracy (recovery: 83.4–103.8%). Furthermore, benefiting from the mesoporous structure and the Zr cluster center as well as the stability, UiO-67 shows great potential to be an excellent adsorbent of SPE for extraction of SAs from other complex matrices.

Unexpected linker-dependent Brønsted acidity in the (Zr)UiO-66 metal organic framework and application to biomass valorization

The functionality of the UiO-66(Zr) linkers affects the number of defects on the Zr6 clusters, leading to differences in the MOFs' Brønsted acidity, which promotes the dehydration of fructose into HMF.

Interplay between structural parameters and reactivity of Zr6-based MOFs as artificial proteases.

Structural parameters influencing the reactivity of metal–organic frameworks (MOF) are challenging to establish. However, understanding their effect is crucial to further develop their catalytic potential. Here, we uncovered a correlation between reaction kinetics and the morphological structure of MOF-nanozymes using the hydrolysis of a dipeptide under physiological pH as model reaction. Comparison of the activation parameters in the presence of NU-1000 with those observed with MOF-808 revealed the reaction outcome is largely governed by the Zr6 cluster. Additionally, its structural environment completely changes the energy profile of the hydrolysis step, resulting in a higher energy barrier ΔG‡ for NU-1000 due to a much larger ΔS‡ term. The reactivity of NU-1000 towards a hen egg white lysozyme protein under physiological pH was also evaluated, and the results pointed to a selective cleavage at only 3 peptide bonds. This showcases the potential of Zr-MOFs to be developed into heterogeneous catalysts for non-enzymatic but selective transformation of biomolecules, which are crucial for many modern applications in biotechnology and proteomics.

Zirconium metal-organic frameworks incorporating tetrathiafulvalene linkers: robust and redox-active matrices for in situ confinement of metal nanoparticles.

Redox-active metal–organic frameworks (MOFs), with highly ordered porous structures and redox tunability, have attracted research interest in the fields of catalysis, energy storage, and electrochemical sensing. However, the chemical lability has limited the application scope of many redox-active MOFs. Herein, we selected stable Zr6 inorganic nodes and redox-active tetrathiafulvalene (TTF)-based linkers to construct two robust, redox-active MOFs, namely compounds 1 ([Zr6(TTFTB)2O8(OH2)8]) and 2 ([Zr6(Me-TTFTB)1.5O4(OH)4(C6H5COO)6]) (TTFTB = tetrathiafulvalene tetrabenzoate; Me-TTFTB = tetrathiafulvalene tetramethylbenzoate). The structure and topology of the MOFs were controlled by tuning the linker conformation through steric effects, resulting in a variety of pore structures from microporous channels (compound 1) to hierarchically micro/mesoporous cages (compound 2). Compound 2 shows high porosity with a BET surface area of 1932 m2 g−1 and strong chemical stability in aqueous solutions with pH ranging from 1 to 12. Furthermore, the reductive TTF moieties allow for in situ generation and stabilization of ultra-small noble metal (Ag, Pd, and Au) nanoparticles by incubating MOFs in the respective metal salt solution. Single crystal structures, TEM images, and pore size distribution data from N2 adsorption measurements indicated that the metal nanoparticles were mostly placed in the small cubic cavities of hierarchically porous compound 2, leaving the large cages open for substrate diffusion. As a proof of concept, Pd NPs@compound 2 was utilized as a heterogeneous catalyst for aerobic oxidation of alcohols, showing noteworthy activity and recyclability.

Fabrication of (4, 10) and (4, 12)-Connected Multifunctional Zirconium Metal-Organic Frameworks for the Targeted Adsorption of a Guest Molecule.

Following the principle of a topology guide, a zirconium MOF (PCN-207) based on the H4TPTA ligand (tetramethyl(4,4',4″,4‴-(pyrazine-2,3,5,6-tetrayl))tetrabenzoic acid) with C2 symmetry and an 8-connected Zr6(μ3-OH)8(OH)8]8+ cluster with D4h symmetry has been synthesized. PCN-206 can also be obtained by modulating the benzoic acid usage to change the flexibility of the H4TPTA ligand. The unique positions of 8-connected Zr6 clusters in the flu and scu networks and the flexibility of the tetratopic primary linker enable the precise insertion of fumarate (FA), 1,4-benzenedicarboxylic acid (H2BDC), and even 2,6-naphthalenedicarboxylic acid (H2NDC) in a one-pot reaction. Auxiliary linkers are used to generate new MOF structures or topologies or to split the pore spaces, which may significantly change the porosity and chemical and physical properties of scaffold MOFs. The results provide a successful strategy for the rational design of multicomponent Zr-MOFs. Because of differences in composition and configuration between structures, PCN-207 shows the highest separation capability of light hydrocarbons; moreover, PCN-206 exhibits the highest adsorption capacity of 2,4-D and DCF among MOFs at present.

Microwave‐Assisted Synthesis as an Efficient Method to Enhance the Catalytic Activity of Zr‐Based Metal Organic Framework UiO‐66 in a Heterocyclization Reaction

AbstractZr‐based metal‐organic frameworks have been considered promising heterogeneous catalysts in various reactions. It has been proven that the defect sites in these frameworks, which result from deficiency of linkers, could act as the reaction active sites. In this work, microwave irradiation was used for rapid synthesis and increasing defects on Zr6 clusters of metal‐organic framework UiO‐66. Powder X‐ray diffraction, thermal gravimetric analysis, and N2 sorption isotherms were performed to characterize and calculate the defect number in the framework. UiO‐66 prepared by microwave method for a few minutes could reach 1.8 missing linkers per cluster. The material with acetic acid as a co‐catalyst showed highly heterogeneous catalytic activity in the solvent‐free heterocyclization of 2,2‐disubstituted 2,3‐dihydroquinazolin‐4(1H)‐ones from anthranilamide and ketones/aldehydes. The synthetic scheme consisted of zirconium cluster catalysed carbonyl group of anthranilamide to achieve the C−N propitious combination and succeeding ring closure process.

Fixing Flexible Arms of Core-Shared Ligands to Enhance the Stability of Metal-Organic Frameworks.

In recent years, more and more research on metal-organic frameworks (MOFs) has focused on exploring their practical applications, where the stability is crucial. Besides the metal-ligand coordination bond, the configuration of the ligand also plays an important role in determining the stability of resulting MOFs. In this work, we demonstrate that fixing flexible arms of core-shared ligands can enhance the stability of their Zr(IV)-MOFs. Two groups, four core-shared tetracarboxylate ligands, 3,3',3″,3‴-(pyrene-1,3,6,8-tetrayltetrakis(benzene-4,1-diyl))tetraacrylate (PTSA4-) and 6,6',6″,6‴-(pyrene-1,3,6,8-tetrayl)tetrakis(2-naphthoate) (PTNA4-) with the pyrene core and 3,3',3″,3‴-((9H-carbazole-1,3,6,8-tetrayl)tetrakis(benzene-4,1-diyl))-tetraacrylate (CTSA4-) and 6,6',6″,6‴-(9H-carbazole-1,3,6,8-tetrayl)tetrakis-(2-naphthoate) (CTNA4-) with the carbazole core are rationally designed. Two ligands in each group have different flexibilities due to the distinct side arms: the styrene arm is flexible, whereas the naphthalene is rigid. Constructed with Zr6 clusters, four 4,8-connected Zr(IV)-MOFs, Zr6O4(OH)8(H2O)4(PTSA)2 (BUT-72) and Zr6O4(OH)8(H2O)4(PTNA)2 (BUT-73) with a sqc-a topologic framework structure and Zr6O4(OH)8(H2O)4(CTSA)2 (BUT-74) and Zr6O4(OH)8(H2O)4(CTNA)2 (BUT-63) with a scu-a structure are obtained, respectively. It is found that the stability of BUT-73 and -63 with the rigid naphthoate-based ligands is significantly enhanced compared with that of BUT-72 and -74 with the flexible phenyl acrylate-based ones. Moreover, stable BUT-63 represents outstanding performance in the molecular recognition of most solvents commonly used in organic synthesis and industrial manufacture.

Tuning the Chemical Environment within the UiO-66-NH2 Nanocages for Charge-Dependent Contaminant Uptake and Selectivity.

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 pKa modeling. A unique feature of the Zr6(μ3-OH)4(μ3-O)4(RCO2)12 cluster is the Zr-bridging oxo/hydroxyl groups, demonstrating several pKa 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.