Seawater contains uranium in surprisingly high quantities that can supply vast energy, if recovered economically. Attempts to design effective sorbents led to the identification of organic functional groups such as amidoximes. Here we report a porous polymer, a polymer of intrinsic microporosity (PIM) with permanent pores that feature amidoxime pendant groups, which is capable of removing more than 90% uranyl [U(VI)] from seawater collected from the Ulleung basin of the East Sea of the Republic of Korea. From this uptake, over 75% was collected in less than six hours, leading to highly feasible field applications. When the seawater was acidified by bubbling CO2 (pH = 5.4), the uptake increased dramatically. Regeneration studies showed full recovery of sorbents and no loss in capture capacity. Our results indicate that successful uranium recovery can be realized by scalable applications of porous polymeric networks and when low cost CO2 is co-administered, uptake can be significantly enhanced.

Solid sorbents for chemisorptive carbon dioxide uptake in post-combustion scenarios require strong binding groups like amines. Post-synthetic impregnation of reactive amines requires large pore volumes. Covalent organic polymers (COPs) are microporous (or narrow mesoporosity) network polymers with physisorptive behavior. Herein as the first of such attempt in porous organic polymers, we modified COP-1, which is an inexpensive, scalable porous polymer for effective amine loading. By expanding the pore of COP-1 through hard templation by silica, the surface area and pore volume are increased by 2.3 and 2.9 times, respectively. It was shown that the increase of pore volume was mostly from pores larger than 5 nm and it correlates well with the silica particle size (12 nm) and the inter-particle pore sizes of silica (31 nm). As a result, amine impregnated Si-COP-1 adsorbs CO2 with the increase of 2.44 at 273 K and 4.06 times at 298 K (at flue gas relevant partial pressure of 0.15 bar) over the parent COP-1. Our results show the possibility of tuning porosity for developing industrially feasible CO2 capturing sorbents.

Designed catalyst poisons can be deliberately added in various reactions for tuning chemoselectivity. In general, the poisons are “transient” selectivity modifiers that are readily leached out during reactions and thus should be continuously fed to maintain the selectivity. In this work, we supported Pd catalysts on a thermochemically stable cross-linked polymer containing diphenyl sulfide linkages, which can simultaneously act as a catalyst support and a “permanent” selectivity modifier. The entire surfaces of the Pd clusters were ligated (or poisoned) by sulfide groups of the polymer support. The sulfide groups capping the Pd surface behaved like a “molecular gate” that enabled exceptionally discriminative adsorption of alkynes over alkenes. H2/D2 isotope exchange revealed that the capped Pd surface alone is inactive for H2 (or D2) dissociation, but in the presence of coflowing acetylene (alkyne), it becomes active for H2 dissociation as well as acetylene hydrogenation. The results indicated that acetylene adsorbs on the Pd surface and enables cooperative adsorption of H2. In contrast, ethylene (alkene) did not facilitate H2–D2 exchange, and hydrogenation of ethylene was not observed. The results indicated that alkynes can induce decapping of the sulfide groups from the Pd surface, while alkenes with weaker adsorption strength cannot. The discriminative adsorption of alkynes over alkenes led to highly chemoselective hydrogenation of various alkynes to alkenes with minimal overhydrogenation and the conversion of side functional groups. The catalytic functions can be retained over a long reaction period due to the high thermochemical stability of the polymer.

Porous polybenzimidazole polymers have been under investigation for high and low pressure CO2 adsorption due to the well-built stability under high pressure and at various temperatures. Pressure swing and temperature swing processes like integrated gasification combined cycle require materials which can operate efficiently at high pressure and high temperature and can remove CO2. In this manuscript we report synthesis, characterization and evaluation of two polybenzimidazole materials (PBI-1 and PBI-2), which were prepared with two different solvents and different cross-linking agents by condensation techniques. Low and high pressure CO2 sorption characteristic of both the materials were evaluated at 273 and 298 K. Thermal gravimetric analysis showed high temperature stability up to 500 °C for the studied materials. PBI-1 has shown very good performance by adsorbing 3 times more (1.8025 mmolg−1 of CO2) than PBI-2 at 0 °C and at low pressures. Despite low surface area results obtained via BET techniques, at 50 bars PBI-1 adsorbed up to 6.08 mmolg−1 of CO2. Studied materials have shown flexible behavior under applied pressure that leads to so-called “gate-opening” adsorption behavior and it makes these materials promising adsorbents of CO2 at high pressures and it is discussed in the manuscript in detail.

Nanoscale zero-valent iron (nZVI), with its reductive potentials and wide availability, offers degradative remediation of environmental contaminants. Rapid aggregation and deactivation hinder its application in real-life conditions. Here, we show that by caging nZVI into the micropores of porous networks, in particular Covalent Organic Polymers (COPs), we dramatically improved its stability and adsorption capacity, while still maintaining its reactivity. We probed the nZVI activity by monitoring azo bond reduction and Fenton type degradation of the naphthol blue black azo dye. We found that depending on the wettability of the host COP, the adsorption kinetics and dye degradation capacities changed. The hierarchical porous network of the COP structures enhanced the transport by temporarily holding azo dyes giving enough time and contact for the nZVI to act to break them. nZVI was also found to be more protected from the oxidative conditions since access is gated by the pore openings of COPs.