Molecular architecture in nanoscale spaces can lead to selective chemical interactions and separation of species with similar sizes and functionality. Substrate specific sorbent chemistry is well known through highly crystalline ordered structures such as zeolites, metal organic frameworks and widely available nanoporous carbons. Size and charge-dependent separation of aqueous molecular contaminants, on the contrary, have not been adequately developed. Here we report a charge-specific size-dependent separation of water-soluble molecules through an ultra-microporous polymeric network that features fluorines as the predominant surface functional groups. Treatment of similarly sized organic molecules with and without charges shows that fluorine interacts with charges favourably. Control experiments using similarly constructed frameworks with or without fluorines verify the fluorine-cation interactions. Lack of a σ-hole for fluorine atoms is suggested to be responsible for this distinct property, and future applications of this discovery, such as desalination and mixed matrix membranes, may be expected to follow.

Effective carbon dioxide (CO2) capture requires solid, porous sorbents with chemically and thermally stable frameworks. Herein, we report two new carbon–carbon bonded porous networks that were synthesized through metal-free Knoevenagel nitrile–aldol condensation, namely the covalent organic polymer, COP-156 and 157. COP-156, due to high specific surface area (650 m2/g) and easily interchangeable nitrile groups, was modified post-synthetically into free amine- or amidoxime-containing networks. The modified COP-156-amine showed fast and increased CO2 uptake under simulated moist flue gas conditions compared to the starting network and usual industrial CO2 solvents, reaching up to 7.8 wt % uptake at 40 °C.

Emerging porous materials like metal organic frameworks (MOFs), (1) covalent organic frameworks (COFs), (2) and porous polymers (3) offer promise in applications such as gas capture, (4) energy storage, (5) or catalysis. (6) Industrial processes that demand such materials prefer high chemical stability as well as scalable and affordable synthesis procedures. Porous polymers with robust C–C bonded networks such as porous aromatic frameworks (PAFs), (7) porous polymer networks (PPNs), (8) and conjugated microporous polymers (CMPs) (3a, 3b) are chemically very stable and have been shown to reach high specific surface areas, leading to great interest in developing network (or highly cross-linked) polymers that feature permanent porosity. (9) Despite the early achievements, the use of prohibitively expensive precious metal catalysts (e.g., Pd) and the less than ideal atom economy prevented a widespread use. In addition, the lack of reactive functional groups covalently tethered on the pore walls is now a great concern, since structures without inherent chemical functionality on the pore walls are behaving similarly to activated carbons or reduced graphene oxide. In order to introduce a suitably reactive functional group, one must resort to postmodification procedures, since high reactivity on a substituent brings chemical diversion in the network building toward extending from the substituent itself. (10) This significantly prohibits chemical tunability (Scheme 1).

Organic compounds, such as covalent organic framework, metal–organic frameworks, and covalent organic polymers have been under investigation to replace the well-known amine-based solvent sorption technology of CO2 and introduce the most efficient and economical material for CO2 capture and storage. Various organic polymers having different function groups have been under investigation both for low and high pressure CO2 capture. However, search for a promising material to overcome the issues of lower selectivity, less capturing capacity, lower mass transfer coefficient and instability in materials performance at high pressure and various temperatures is still ongoing process. Herein, we report synthesis of six covalent organic polymers (COPs) and their CO2, N2, and CH4 adsorption performances at low and high pressures up to 200 bar. All the presented COPs materials were characterized by using elemental analysis method, Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (NMR) spectroscopy techniques. Physical properties of the materials such as surface areas, pore volume and pore size were determined through BET analysis at 77 K. All the materials were tested for CO2, CH4, and N2 adsorption using state of the art equipment, magnetic suspension balance (MSB). Results indicated that, amide based material i.e. COP-33 has the largest pore volume of 0.2 cm2/g which can capture up to the maximum of 1.44 mmol/g CO2 at room temperature and at pressure of 10 bar. However, at higher pressure of 200 bar and 308 K ester-based compound, that is, COP-35 adsorb as large as 144 mmol/g, which is the largest gas capturing capacity of any COPs material obtained so far. Importantly, single gas measurement based selectivity of COP-33 was comparatively better than all other COPs materials at all condition. Nevertheless, overall performance of COP-35 rate of adsorption and heat of adsorption has indicated that this material can be considered for further exploration as efficient and cheaply available solid sorbent material for CO2 capture and separation.

Porous solid sorbents have been investigated for the last few decades to replace the costly amine solution and explore the most efficient and economical material for CO2 capture and storage. Covalent organic polymers (COPs) have been recently introduced as promising materials to overcome several issues associated with the solid sorbents such as thermal stability and low gas capturing capacity. Herein we report the synthesis of four COPs and their CO2, N2 and CH4 uptakes. All the presented COP materials were characterized by using an elemental analysis method, Fourier transform infrared spectroscopy (FTIR) and solid state nuclear magnetic resonance (NMR) spectroscopy techniques. The physical properties of the materials such as surface area, pore volume and pore size were determined by BET analysis at 77 K. All the materials were tested for CO2, CH4 and N2 adsorption through a volumetric method using magnetic sorption apparatus (MSA). Among the presented materials, COP-118 has the highest surface area of 473 m2 g−1 among the other four materials and has shown excellent performance by capturing 2.72 mmol g−1 of CO2, 1.002 mmol g−1 of CH4 and only 0.56 mmol g−1 of N2 at 298 K and 10 bars. However the selectivity of another material, COP-117-A, was better than that of COP-118. Nevertheless, the overall performance of the latter has indicated that this material can be considered for further exploration as an efficient and cheaply available solid sorbent compound for CO2 capture and separation.