Porous polymers. For an effective CO2 capture and separation, we built over 200 nanoporous network polymers (Covalent Organic Polymers, COPs). COP-1 recorded the highest CO2 capacity ever measured in any materials to date (128 mmol/g, J. Mater. Chem. 2012, 22, 8431). Targeting the pre-combustion conditions, COP-2 shows a near infinite selectivity for CO2 over hydrogen gas. COPs-68-81 (Azo-COPs) shows a unique, previously unknown, N2-phobic behavior (Nature Commun., 2013, 4, 1357 and two subsequent papers in Chem. Eur. J.) and COP-40 is easily made into membranes for continuous CO2 separation. COP-83 has a capacity of 5 mmol/g at 298 K and 1 bar (J. Mater. Chem. A 2014, 2, 12507), and COP-97 shows an uptake of 8 % (w/w) CO2 in 2 minutes from a simulated flue gas mixture (CO2 15%, H2O 3.8%, He 81.2%, 40 oC, flow rate: 80 mL/min) (Faraday Disc. 2015, 183, 401-412). Box-COPs (COPs 93-95) are stable up to a staggering 600 oC and could be formed into films (Chem. Mater. 2014, 26, 6729). Using COPs 114 and 115 we controlled the amine amount and chain length to observe a concerted CO2 binding mechanism (Phys. Chem. Chem. Phys. 2016, 18, 14177-14181). COPs with ester and amide functionalities also found to favor CO2 adsorption, particularly at high pressures (ACS Appl. Mater. Interfaces, 2016, 8, 20772–20785). Our results point to an ideal nanoporous structure to be made from a highly porous, inexpensive, physisorptive solid, which is chemically modified with chemisorptive functionalities such as amines (see our tutorial review at ChemSusChem, 2017, 10, 1303). Amidoximes. We have discovered CO2-philic properties of amidoxime functional groups for the first time. Our initial studies focused on the proof of the concept, where molecular amidoximes are found to capture CO2 better than the industrial standard, monoethanolamine, MEA (Energy Environ. Sci., 2011, 4, 4528). Introducing amidoxime functionality to porous polymeric membranes enhanced CO2 capture and selectivity significantly (Chem. Comm., 2012, 48, 9989). Inorganic sorbents. Layered double hydroxides (hydrotalcites) are effective high temperature CO2 sorbents with poor stability and recyclability. Trivalent cations (Al3+) are substituted with gallium for a reversible and robust CO2 sorbent (Chem. Mater., 2009, 21, 3473). Lithium silicate was promoted with TiO2 nanotubes for a reusable high temperature CO2 sorbent with fast kinetics of adsorption – desorption cycles (Ind. Eng. Chem. Res., 2017, 56, 3413).

Charge dependent separation of organic molecules from water. Ultramicroporous fluoropolymer network (COP-99) was developed from a self-condensation reaction of perfluoro hydroquinone and shown to separate water-soluble organics by their size and charges (Nature Commun. 2016, 7, 13377). This nanoporous material is the first to selectively pull dyes and other compounds from water based on their charge and size. The fluorine-cation interaction was found to be the main driving force for this unusual behavior. Nano-magnetic separations for water treatment. A new method for making magnetite (Fe3O4) nanocrystals was developed (Chem. Comm., 2004, 2306) and these were used to show size dependent magnetic behavior and enhanced arsenic affinity (Science, 2006, 314, 964). Unprecedented low temperature phase transition (Nature Mater., 2007, 7, 130), magnetic separations (Chem. Eng. Sci., 2009, 64, 2510) and analytical ultracentrifugations (ACS Nano, 2008, 2, 311) were also made possible by these uniform magnetite nanocrystals. An affordable and accessible arsenic removal technology that is based on magnetic nanoparticles and an open source concept to produce them was introduced through the use of household items such as edible oils, rust, vinegar (Environ. Geochem. Health, 2010, 32, 327). We then synthesized barium hexaferrite (BHF) nanoparticles and tested them for the arsenic removal (J. Nanopart. Res. 2012, 14, 881). Subsequently, we developed an inexpensive method to synthesize BHF nanofibers. The BHF fibers are the thinnest ever in the literature and the goal is to make a mesh out of these in solving the leaching problem for magnetic nanoparticle based water treatment procedures (J. Nanopart. Res. 2014, 16, 2787). Shape controlled synthesis of nanoparticles in porous polymeric frameworks for water treatment. Shape and size variation for nanoparticles is limited to surfactant-controlled synthesis. We developed one of the first methods to control nanoparticle growth by locking them into the pores of porous polymers (J. Mater. Chem. A 2015, 3, 15489). Using same approach we installed nanoscale zero valent iron (nZVI) into COP networks for effective degradation of organic pollutants (J. Mater. Chem. A 2016, 4, 632-639). Uranium capture from seawater. Oceans contain vast amounts of fissile uranium but there is no economically feasible sorbent to extract them. Our amidoxime based sorbents showed the fastest and the highest Uranium uptake with multiple cycles of regeneration and reuse (RSC Adv. 2016, 6, 45968-45976). Precious metal capture from electronic waste. Phenazine COPs are designed for capturing gold and platinum from electronic waste. High selectivity and low cost of the sorbent enables commercial development.

Nanoporous polymers as base catalysts. Porous polymers contain basic heteroatoms like nitrogens which can act as catalysts. We found that base catalyzed reactions such as Strecker synthesis can be effectively promoted by box-COPs without the need for metals (Adv. Sustain. Syst. 2017, 1, 1700089). Nanoporous polymers as nanoparticle caging hosts for gas conversions. We showed that common transition metal nanoparticle based composites of porous polymers can catalyze probe reactions such as CO oxidation as good as platinum (J. Mater. Chem. A 2015, 3, 15489). Acetylene can be selectively reduced to ethylene using metal doped-COP-6 networks (ACS Catal. 2016, 6, 2435-2442). Dry reforming of methane by Nickel catalysts. Nickel and molybdenum nanoparticles were deposited on MgO support for coke resistant dry reforming of methane. Nanowire catalysis. Well defined VO2 nanowires on sapphire (α-Al2O3) substrates (Nano Lett., 2009, 9, 4138) were used as supports for noble metal catalysts to monitor nano-sized changes of the structures during gas catalysis with in-situ grazing incidence X-Ray scattering (GISAXS) technique.

Methane storage in porous polymers. Inexpensive nanoporous polymers were constructed from widely available building blocks to deliver high Adsorbed Natural Gas (ANG) capacity when cycled between 5 and 100 bar pressures. Nanoscale chemistry for high performance Li-ion batteries. Cobalt oxide (Co3O4) nanoparticles are grown inside the pores of COPs providing caging effect for effective expansion and contraction in Li-ion battery charge/discharge, leading to more than 300 cycles without deterioration (J. Mater. Chem. A 2015, 3, 15489). Flexible Li-ion batteries with half mm thickness were constructed (Nano Lett., 2015, 15, 2350).