Debanjan Chakraborty

Ultralow Parasitic Energy for Postcombustion CO2 Capture Realized in a Nickel Isonicotinate Metal–Organic Framework with Excellent Moisture Stability

Metal-organic frameworks (MOFs) have attracted significant attention as solid sorbents in gas separation processes for low-energy postcombustion CO2 capture. The parasitic energy (PE) has been put forward as a holistic parameter that measures how energy efficient (and therefore cost-effective) the CO2 capture process will be using the material. In this work, we present a nickel isonicotinate based ultramicroporous MOF, 1 [Ni-(4PyC)2·DMF], that has the lowest PE for postcombustion CO2 capture reported to date. We calculate a PE of 655 kJ/kg CO2, which is lower than that of the best performing material previously reported, Mg-MOF-74. Further, 1 exhibits exceptional hydrolytic stability with the CO2 adsorption isotherm being unchanged following 7 days of steam-treatment (>85% RH) or 6 months of exposure to the atmosphere. The diffusion coefficient of CO2 in 1 is also 2 orders of magnitude higher than in zeolites currently used in industrial scrubbers. Breakthrough experiments show that 1 only loses 7% of its maximum CO2 capacity under humid conditions.

Strategically designed azolyl-carboxylate MOFs for potential humid CO2 capture

Development of solid sorbents with optimal CO2 capture characteristics is key to improving the efficiency of PSA based CO2 separation. Of the several potential sorbents, metal organic frameworks (MOFs) hold a key niche. This is owing to their modular tunable structures and manipulatable adsorption sites. Yet, developing a MOF that meets the multiple demands of a gas-separation sorbent remains a challenge. Particularly, tuning them to adsorb CO2 over the more polar water is quite difficult. The presence of highly polarizing metal centers and oxygen-rich sites in MOFs makes it difficult to retain their CO2 adsorption capacities under humid gas streams. However, tailoring the organic framework to incorporate humid CO2 capture properties should be feasible. Along these lines, here we have developed a family of iso-structural MOFs built from bi-functional ligands that carry basic azolyl and chelating carboxylate groups together. Importantly, the framework is built by employing acetate moieties as ‘modulators’; they provide a hydrophobic lining to the pore-walls. This not only enables selective adsorption of CO2, but also helps retain about 80% of the capture capacity even upon exposure to 75% RH. Along with its other advantageous features: high CO2 uptake and selectivity (3 mmol g−1 and s(CO2–N2) = ∼500 for 85N2:15CO2@303 K); surface area: ∼700 m2 g−1, working capacity: 2.6 mmol g−1; optimal HOA (22–30 kJ mol−1) and CO2 kinetics (Dc = 1.02 × 10−8 m2 s−1), these MOFs can qualify as efficient candidates for humid CO2 capture. Furthermore, we identify the most-favorable CO2 adsorption sites via simulated annealing methods, from which the presence of polarized CO2 molecules located adjacent to the π-electron rich pore walls can be seen. Importantly, these polarized molecules form T-shaped configurations among themselves via C(δ+ve)⋯O(δ−ve) interactions resembling those found in solid CO2, a cooperative feature that is not observed in the other CO2 molecules in the structure, which are not proximal to the polarizing walls.

Stratification approach for forest cover type and landuse mapping using IRS-1A LISS-II data — A case study

Indian Remote Sensing Satellite-1A (IRS-1A) LISS-II data of 24th Nov., 1988 was analysed digitally to differentiate three density classes viz. dense/closed forest, open forest and degraded forest within each vegetation type in the district, Jalpaiguri, West Bengal. Stratification approach was used to classify separately forest cover into pure sal forests, mixed forests, riverine forests along with man-made sal/teak plantations. In this approach the forested and non-forested areas were classified separately through supervised classification techniques using maximum likelihood algorithm using VAX 11/780 based VIPS-32 Image Processing software. Later the two classified outputs were composited to provide entire area of the district. The forest cover of the district was 1420.89 sq. km, (22.82 percent). Other broad landuse/landcover dominant in the district include agricultural areas.(45.20 percent) and tea gardens (10.49 percent). The accuracy of the classified output was estimated to be 90 percent for forested areas and 85 percent in case of other landuse/landcover classes.

Preferential Adsorption of CO2 in an Ultramicroporous MOF with Cavities Lined by Basic Groups and Open-Metal Sites

Here, we present a new ultramicroporous Cu2 paddlewheel based MOF. This ultramicroporous MOF has most of the features such as porosity (BET surface area = 945 m2/g), CO2 capacity (3.5 mmol/g at ambient temperature and pressure), CO2/N2 selectivity (sCO2/N2 = 250), and fast CO2 diffusion kinetics ( Dc = 2.25 × 10-9 m2/s), comparable to some of the other high-performing ultramicroporous MOFs, with strong binding sites. Typically, such MOFs exhibit strong CO2-framework interactions (evidenced from a heat of adsorption ≥ 38 kJ/mol). However, the MOF explained here, despite having channels lined by the amine and the open-metal sites, possesses only a moderate CO2-framework interaction (HOA = 26 kJ/mol). Using periodic DFT, we have probed this counterintuitive observation.

Ultra-low parasitic energy for post-combustion CO2 capture realized in a nickel isonicotinate MOF with excellent moisture stability

Metal-organic frameworks (MOFs) have attracted significant attention as solid sorbents in gas separation processes for low-energy postcombustion CO2 capture. The parasitic energy (PE) has been put forward as a holistic parameter that measures how energy efficient (and therefore cost-effective) the CO2 capture process will be using the material. In this work, we present a nickel isonicotinate based ultramicroporous MOF, 1 [Ni-(4PyC)2·DMF], that has the lowest PE for postcombustion CO2 capture reported to date. We calculate a PE of 655 kJ/kg CO2, which is lower than that of the best performing material previously reported, Mg-MOF-74. Further, 1 exhibits exceptional hydrolytic stability with the CO2 adsorption isotherm being unchanged following 7 days of steam-treatment (>85% RH) or 6 months of exposure to the atmosphere. The diffusion coefficient of CO2 in 1 is also 2 orders of magnitude higher than in zeolites currently used in industrial scrubbers. Breakthrough experiments show that 1 only loses 7% of its maximum CO2 capacity under humid conditions.

Anthracene-Resorcinol Derived Covalent Organic Framework as Flexible White Light Emitter

The ordered modular structure of a covalent organic framework (COF) facilitates the selective incorporation of electronically active segments that can be tuned to function cooperatively. This designability inspires developing COF-based single-source white light emitters, required in next-generation solid-state lighting. Here, we present a new anthracene-resorcinol-based COF exhibiting white light emission. The keto-enol tautomers present in the COF give rise to dual emission, which can be tuned by the O-donor and N-donor solvents. Importantly, when suspended in a solid polymer matrix, this dual emission is retained as both tautomers coexist. A mere 0.32 wt % loading of the COF in poly(methyl methacrylate) (PMMA) gives a solvent-free film with intense white light emission (CIE coordinates (0.35, 0.36)). From steady-state and time-resolved studies, the mechanism of the white light emission has been unambiguously assigned to fluorescence, with the blue emission originating from the π-stacked columns of anthracene, and the mixture of red and green from the keto-enol tautomerized resorcinol units. The study introduces the COF as a new class of readily processable, single-source white light emitter.

Ultralow Parasitic Energy for Postcombustion CO 2 Capture Realized in a Nickel Isonicotinate Metal–Organic Framework with Excellent Moisture Stability

Metal-organic frameworks (MOFs) have attracted significant attention as solid sorbents in gas separation processes for low-energy postcombustion CO2 capture. The parasitic energy (PE) has been put forward as a holistic parameter that measures how energy efficient (and therefore cost-effective) the CO2 capture process will be using the material. In this work, we present a nickel isonicotinate based ultramicroporous MOF, 1 [Ni-(4PyC)2·DMF], that has the lowest PE for postcombustion CO2 capture reported to date. We calculate a PE of 655 kJ/kg CO2, which is lower than that of the best performing material previously reported, Mg-MOF-74. Further, 1 exhibits exceptional hydrolytic stability with the CO2 adsorption isotherm being unchanged following 7 days of steam-treatment (>85% RH) or 6 months of exposure to the atmosphere. The diffusion coefficient of CO2 in 1 is also 2 orders of magnitude higher than in zeolites currently used in industrial scrubbers. Breakthrough experiments show that 1 only loses 7% of its maximum CO2 capacity under humid conditions.