Briana Aguila

Imparting amphiphobicity on single-crystalline porous materials

The sophisticated control of surface wettability for target-specific applications has attracted widespread interest for use in a plethora of applications. Despite the recent advances in modification of non-porous materials, surface wettability control of porous materials, particularly single crystalline, remains undeveloped. Here we contribute a general method to impart amphiphobicity on single-crystalline porous materials as demonstrated by chemically coating the exterior of metal-organic framework (MOF) crystals with an amphiphobic surface. As amphiphobic porous materials, the resultant MOF crystals exhibit both superhydrophobicity and oleophobicity in addition to retaining high crystallinity and intact porosity. The chemical shielding effect resulting from the amphiphobicity of the MOFs is illustrated by their performances in water/organic vapour adsorption, as well as long-term ultrastability under highly humidified CO2 environments and exceptional chemical stability in acid/base aqueous solutions. Our work thereby pioneers a perspective to protect crystalline porous materials under various chemical environments for numerous applications.

A bifunctional metal–organic framework featuring the combination of open metal sites and Lewis basic sites for selective gas adsorption and heterogeneous cascade catalysis

A bifunctional MOF (JUC-199) featuring dual functionality, open metal sites (Zn2+) and Lewis basic sites (–NH2), has been successfully synthesized using a custom-designed ligand. JUC-199 demonstrated good selective gas sorption behaviours with IAST selectivity values of 9, 30, 37 and 64 at 298 K and 101 kPa for CO2/CH4, CO2/N2, C2H6/CH4 and C2H4/CH4 respectively; surpassing those of most MOFs reported thus far. Moreover, JUC-199 can serve as a heterogeneous cascade catalyst to efficiently catalyse the tandem one-pot deacatalization-Knoevenagel condensation reaction.

Retracted Article: Potential applications of functional porous organic polymer materials

Porous materials are important in established processes, such as catalysis and molecular separations, and in emerging technologies for energy and health. Porous organic polymers (POPs), a class of highly crosslinked, amorphous polymers possessing nanopores, have recently emerged as a versatile platform for potential applications. As an emerging material, POPs offer high flexibility for the molecular design and post-synthetic modification of their conjugated skeletons and nanopores. They have shown great potential for challenging energy and environmental issues, as exemplified by their excellent performance in gas storage/separation, catalysis, environmental remediation, and sensing. This review article summarizes the recent frontiers of functional exploration and potential applications of porous organic polymers.

Efficient Mercury Capture Using Functionalized Porous Organic Polymer

The primary challenge in materials design and synthesis is achieving the balance between performance and economy for real-world application. This issue is addressed by creating a thiol functionalized porous organic polymer (POP) using simple free radical polymerization techniques to prepare a cost-effective material with a high density of chelating sites designed for mercury capture and therefore environmental remediation. The resulting POP is able to remove aqueous and airborne mercury with uptake capacities of 1216 and 630 mg g-1 , respectively. The material demonstrates rapid kinetics, capable of dropping the mercury concentration from 5 ppm to 1 ppb, lower than the US Environmental Protection Agencys drinking water limit (2 ppb), within 10 min. Furthermore, the material has the added benefits of recyclability, stability in a broad pH range, and selectivity for toxic metals. These results are attributed to the materials physical properties, which include hierarchical porosity, a high density of chelating sites, and the materials robustness, which improve the thiol availability to bind with mercury as determined by X-ray photoelectron spectroscopy and X-ray absorption fine structure studies. The work provides promising results for POPs as an economical material for multiple environmental remediation applications.

Functionalized Porous Aromatic Framework for Efficient Uranium Adsorption from Aqueous Solutions

We demonstrate the successful functionalization of a porous aromatic framework for uranium extraction from water as exemplified by grafting PAF-1 with the uranyl chelating amidoxime group. The resultant amidoxime-functionalized PAF-1 (PAF-1-CH2AO) exhibits a high uranium uptake capacity of over 300 mg g-1 and effectively reduces the uranyl concentration from 4.1 ppm to less than 1.0 ppb in aqueous solutions within 90 min, well below the acceptable limit of 30 ppb set by the US Environmental Protection Agency. The local coordination environment of uranium in PAF-1-CH2AO is revealed by X-ray absorption fine structure spectroscopic studies, which suggest the cooperative binding between UO22+ and adjacent amidoxime species.

Removal of Pertechnetate‐Related Oxyanions from Solution Using Functionalized Hierarchical Porous Frameworks

Efficient and cost-effective removal of radioactive pertechnetate anions from nuclear waste is a key challenge to mitigate long-term nuclear waste storage issues. Traditional materials such as resins and layered double hydroxides (LDHs) were evaluated for their pertechnetate or perrhenate (the non-radioactive surrogate) removal capacity, but there is room for improvement in terms of capacity, selectivity and kinetics. A series of functionalized hierarchical porous frameworks were evaluated for their perrhenate removal capacity in the presence of other competing anions.

Porous Ionic Polymers as a Robust and Efficient Platform for Capture and Chemical Fixation of Atmospheric CO2

Direct use of atmospheric CO2 as a C1 source to synthesize high-value chemicals through environmentally benign processes is of great interest, yet challenging. Porous heterogeneous catalysts that are capable of simultaneously capturing and converting CO2 are promising candidates for such applications. Herein, a family of organic ionic polymers with nanoporous structure, large surface area, strong affinity for CO2 , and very high density of catalytic active sites (halide ions) was synthesized through the free-radical polymerization of vinylfunctionalized quaternary phosphonium salts. The resultant porous ionic polymers (PIPs) exhibit excellent activities in the cycloaddition of epoxides with atmospheric CO2 , outperforming the corresponding soluble phosphonium salt analogues and ranking among the highest of known metal-free catalytic systems. The high CO2 uptake capacity of the PIPs facilitates the enrichment of CO2 molecules around the catalytic centers, thereby benefiting its conversion. We have demonstrated for the first time that atmospheric CO2 can be directly converted to cyclic carbonates at room temperature using a heterogeneous catalytic system under metal-solvent free conditions. Moreover, the catalysts proved to be robust and fully recyclable, demonstrating promising potential for practical utilization for the chemical fixation of CO2 . Our work thereby paves a way to the advance of PIPs as a new type of platform for capture and conversion of CO2 .

A Stable Metal–Organic Framework Featuring a Local Buffer Environment for Carbon Dioxide Fixation

A majority of metal-organic frameworks (MOFs) fail to preserve their physical and chemical properties after exposure to acidic, neutral, or alkaline aqueous solutions, therefore limiting their practical applications in many areas. The strategy demonstrated herein is the design and synthesis of an organic ligand that behaves as a buffer to drastically boost the aqueous stability of a porous MOF (JUC-1000), which maintains its structural integrity at low and high pH values. The local buffer environment resulting from the weak acid-base pairs of the custom-designed organic ligand also greatly facilitates the performance of JUC-1000 in the chemical fixation of carbon dioxide under ambient conditions, outperforming a series of benchmark catalysts.

A bifunctional covalent organic framework as an efficient platform for cascade catalysis

A bifunctional covalent organic framework (COF) has been illustrated in the context of partial metalation of a highly porous and chemically robust pyridine containing COF (COF-TpPa-Py) with Pd species and by taking advantage of the base catalytic behavior of pyridine. The resultant bifunctionalized COF exhibits excellent performance in catalyzing one-pot cascade aerobic oxidation–Knoevenagel condensation reactions, outperforming the corresponding homogeneous and porous organic polymer based catalytic systems, thereby opening a new avenue for multifunctional COFs as a promising platform for heterogeneous cascade catalysis.

Covalent Organic Frameworks as a Decorating Platform for Utilization and Affinity Enhancement of Chelating Sites for Radionuclide Sequestration

The potential consequences of nuclear events and the complexity of nuclear waste management motivate the development of selective solid-phase sorbents to provide enhanced protection. Herein, it is shown that 2D covalent organic frameworks (COFs) with unique structures possess all the traits to be well suited as a platform for the deployment of highly efficient sorbents such that they exhibit remarkable performance, as demonstrated by uranium capture. The chelating groups laced on the open 1D channels exhibit exceptional accessibility, allowing significantly higher utilization efficiency. In addition, the 2D extended polygons packed closely in an eclipsed fashion bring chelating groups in adjacent layers parallel to each other, which may facilitate their cooperation, thereby leading to high affinity toward specific ions. As a result, the amidoxime-functionalized COFs far outperform their corresponding amorphous analogs in terms of adsorption capacities, kinetics, and affinities. Specifically, COF-TpAb-AO is able to reduce various uranium contaminated water samples from 1 ppm to less than 0.1 ppb within several minutes, well below the drinking water limit (30 ppb), as well as mine uranium from spiked seawater with an exceptionally high uptake capacity of 127 mg g-1 . These results delineate important synthetic advances toward the implementation of COFs in environmental remediation.