Many environmental pollutants inherently exist in their anionic forms and are therefore highly mobile in natural water systems. Cationic framework materials that can capture those pollutants are highly desirable but scarcely reported. Here we present a mesoporous cationic thorium-based MOF (SCU-8) containing channels with a large inner diameter of 2.2 nm and possessing a high surface area of 1360 m2 g−1. The anion-exchange properties of SCU-8 were explored with many anions including small oxo anions like ReO4 − and Cr2O7 2− as well as anionic organic dyes like methyl blue and the persistent organic pollutant, perfluorooctane sulfonate (PFOS). Both fast uptake kinetics and great sorption selectivity toward PFOS are observed. The underlying sorption mechanism was probed using quantum mechanical and molecular dynamics simulations. These computational results reveal that PFOS anions are immobilized in SCU-8 by driving forces including electrostatic interactions, hydrogen bonds, hydrophobic interactions, and van der Waals interactions at different adsorption stages.

Metal-organic frameworks (MOFs) based on zirconium phosphonates exhibit superior chemical stability suitable for applications under harsh conditions. These compounds mostly exist as poorly crystallized precipitates, and precise structural information has therefore remained elusive. Furthermore, a zero-dimensional zirconium phosphonate cluster acting as secondary building unit has been lacking, leading to poor designability in this system. Herein, we overcome these challenges and obtain single crystals of three zirconium phosphonates that are suitable for structural analysis. These compounds are built by previously unknown isolated zirconium phosphonate clusters and exhibit combined high porosity and ultrastability even in fuming acids. SZ-2 possesses the largest void volume recorded in zirconium phosphonates and SZ-3 represents the most porous crystalline zirconium phosphonate and the only porous MOF material reported to survive in aqua regia. SZ-2 and SZ-3 can effectively remove uranyl ions from aqueous solutions over a wide pH range, and we have elucidated the removal mechanism.

Although comprehensive progress has been made in the area of coordination polymer (CP)/metal-organic framework (MOF)-based proton-conducting materials over the past decade, searching for a CP/MOF with stable, intrinsic, high anhydrous proton conductivity that can be directly used as a practical electrolyte in an intermediate-temperature proton-exchange membrane fuel cell assembly for durable power generation remains a substantial challenge. Here, we introduce a new proton-conducting CP, (NH)[Zr(HPO)] (ZrP), which consists of one-dimensional zirconium phosphate anionic chains and fully ordered charge-balancing NH cations. X-ray crystallography, neutron powder diffraction, and variable-temperature solid-state NMR spectroscopy suggest that protons are disordered within an inherent hydrogen-bonded infinite chain of acid-base pairs (N-H···O-P), leading to a stable anhydrous proton conductivity of 1.45 × 10 S·cm at 180 °C, one of the highest values among reported intermediate-temperature proton-conducting materials. First-principles and quantum molecular dynamics simulations were used to directly visualize the unique proton transport pathway involving very efficient proton exchange between NH and phosphate pairs, which is distinct from the common guest encapsulation/dehydration/superprotonic transition mechanisms. ZrP as the electrolyte was further assembled into a H/O fuel cell, which showed a record-high electrical power density of 12 mW·cm at 180 °C among reported cells assembled from crystalline solid electrolytes, as well as a direct methanol fuel cell for the first time to demonstrate real applications. These cells were tested for over 15 h without notable power loss.

Global environmental challenges especially nuclear pollution pose a great threat to human health and public safety. Metal-organic frameworks (MOFs) with high surface area and excellent stability are potential candidates for the remediation of nuclear pollution. Herein, a ZIF-8-based polyacrylonitrile (PAN) fibrous filter was prepared by an in situ hydrothermal treatment of fibrous filters consisting of PAN, poly(vinylpyrrolidone) (PVP), and zinc ions with an electrospinning method. In the process of hydrothermal treatment, PVP can be extracted from the PAN nanofibers and result in porous structures. Benefiting from these porous structures, the in situ ZIF-8/PAN filters demonstrated a high adsorption capacity of U(VI) (530.3 mg g at pH = 3.0). The extended X-ray absorption fine structure revealed that the adsorption mechanism demonstrated surface complexation between U(VI) and 2-methylimidazole. Furthermore, the adsorption device was fabricated, and the dynamic adsorption shows that in situ ZIF-8/PAN is a promising material for treating the nuclear wastewater. The present work may provide a new strategy to fabricate MOFs into functional devices to remediate the increasing global environmental concerns.

Actinide based metal-organic frameworks (MOFs) are unique not only because compared to the transition-metal and lanthanide systems they are substantially less explored, but also owing to the uniqueness of actinide ions in bonding and coordination. Now a 3D thorium-organic framework (SCU-11) contains a series of cages with an effective size of ca. 21×24 Å. Th in SCU-11 is 10-coordinate with a bicapped square prism coordination geometry, which has never been documented for any metal cation complexes. The bicapped position is occupied by two coordinated water molecules that can be removed to afford a very unique open Th site, confirmed by X-ray diffraction, color change, thermogravimetry, and spectroscopy. The degassed phase (SCU-11-A) exhibits a Brunauer-Emmett-Teller surface area of 1272 m g , one of the highest values among reported actinide materials, enabling it to sufficiently retain water vapor, Kr, and Xe with uptake capacities of 234 cm g , 0.77 mmol g , 3.17 mmol g , respectively, and a Xe/Kr selectivity of 5.7.

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The chemisorptive enantioselectivity of propylene oxide is examined on Pd(111) surfaces templated by chiral 2-methylbutanoate and 2-aminobutanoate species. It has been found previously that chiral propylene oxide is chemisorbed enantiospecifically onto Pd(111) surfaces modified by either (R)-or (S)-2-butoxide. The enantiomeric excess (ee) varied with template coverage, reaching a maximum of ∼31%. Templating the surface using 2-methylbutanoate, where the chiral center is identical to that in the 2-butoxide species, but is now anchored to the surface by a carboxylate rather than an alkoxide linkage, shows no enantiospecificity. The enantioselectivity is restored when the methyl group is replaced by an amine group, where a maximum ee value of ∼27% is found. DFT calculations and infrared measurements suggest that the structures of the butyl group on the surface are similar for both 2-butoxide and 2-methylbutanoate species, implying that gross conformational changes are not responsible for differences in chemisorptive enantioselectivity. There is no clear correlation between the location of the chiral center and enantioselectivity, suggesting that differences in the template adsorption site are also not responsible for the lack of enantioselectivity. It is proposed that the 2-butyl group in 2-methylbutanoate species is less rigidly bonded to the surface than that in 2-butoxides, allowing the chiral center to rotate azimuthally. It is postulated that the role of the amino group in 2-aminobutanoate species is to anchor the chiral group to the surface to inhibit azimuthal rotation.

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