Mohammad Gulam Rabbani

A 2D Mesoporous Imine‐Linked Covalent Organic Framework for High Pressure Gas Storage Applications

Hole-some mixture: A 2D mesoporous covalent organic framework (see figure) featuring expanded pyrene cores and linked by imine linkages has a high surface area (SA(BET) = 2723 m(2)  g(-1)) and exhibits significant gas storage capacities under high pressure, which make this class of material very promising for gas storage applications.

Pyrene-directed growth of nanoporous benzimidazole-linked nanofibers and their application to selective CO2 capture and separation

A pyrene-based benzimidazole-linked polymer (BILP-10) has been synthesized by the co-condensation of 1,3,6,8-tetrakis(4-formylphenyl)pyrene and 1,2,4,5-benzenetetramine tetrahydrochloride in dimethylformamide. The use of pyrene as a molecular building unit leads to the formation of self-assembled nanofibers that have moderate surface area (SABET = 787 m2 g−1) and very high CO2/N2 (128) and CO2/CH4 (18) selectivities at 273 K. Furthermore, results from gas uptake measurements indicate that BILP-10 can store significant amounts of CO2 (4.0 mmol at 273 K/1.0 bar) and H2 (1.6 wt% at 77 K/1.0 bar) with respective isosteric heats of adsorption of 38.2 and 9.3 kJ mol−1 which exceed all of the previously reported values for BILPs and are among the highest values reported to date for unmodified porous organic polymers. Under high pressure settings, BILP-10 displays moderate uptakes of H2 (27.3 g L−1, 77 K/40 bar), CH4 (72 L L−1, 298 K/40 bar), and CO2 (13.3 mmol g−1, 298 K/40 bar). The unusually high CO2 and H2 binding affinities of BILP-10 are presumably facilitated by the amphoteric pore walls of the polymer that contain imidazole moieties and the predominant microporous nature.

Impact of post-synthesis modification of nanoporous organic frameworks on small gas uptake and selective CO2 capture

Porous organic polymers containing nitrogen-rich building units are among the most promising materials for selective CO2 capture and separation applications that impact the environment and the quality of methane and hydrogen fuels. In this study, we report on post-synthesis modification of nanoporous organic frameworks (NPOFs) and its impact on gas storage (H2, CH4, CO2) and selective CO2 binding over N2 and CH4 under ambient conditions. The synthesis of NPOF-4 was accomplished via acid catalyzed cyclotrimerization reaction of 1,3,5,7-tetrakis(4-acetylphenyl)adamantane in ethanol/xylenes. NPOF-4 is microporous and has high surface area (SABET = 1249 m2 g−1). Post-synthesis modification of NPOF-4 by nitration afforded NPOF-4-NO2 and its subsequent reduction resulted in an amine-functionalized framework NPOF-4-NH2 that exhibits improved gas storage capacities and very high CO2/N2 (139) and CO2/CH4 (15) selectivities compared to NPOF-4.

Synthesis of highly porous borazine-linked polymers and their application to H2, CO2, and CH4 storage

The synthesis of highly porous borazine-linked polymers (BLPs) and their gas uptakes are reported. BLPs exhibit high surface areas up to 2866 m2 g−1 and can store significant amounts of H2 (1.93 wt%) and CO2 (12.8 wt%) at 77 K and 273 K, respectively at 1.0 bar with respective isosteric heats of adsorption of 6.0 and 25.2 kJ mol−1.

Benzothiazole- and benzoxazole-linked porous polymers for carbon dioxide storage and separation

Incorporation of CO2-philic heteroatoms (i.e. N, S, and O) into porous organic polymers has been instrumental in achieving selective CO2 capture. Here, we report the synthesis of porous benzothiazole and benzoxazole linked polymers which have sulfur and oxygen atoms, respectively, in addition to the nitrogen functionality. Their structural properties have been analyzed and compared to their analogous benzimidazole linked polymers which have only nitrogen heteroatoms. The polymers exhibit high surface areas (SABET = 698–1011 m2 g−1), high physicochemical stability, and considerable CO2 storage capacity. Low pressure gas uptake experiments were used to calculate the binding affinity of small gas molecules and revealed that the polymers have high heats of adsorption (Qst) for CO2 (28.7–33.6 kJ mol−1). Comparison of CO2 uptakes and Qst values of benzothiazole-, benzoxazole- and benzimidazole-linked polymers demonstrated that smaller pores facilitate CO2 adsorption with higher Qst values and the total CO2 uptake capacity mainly depends on the surface areas provided that the pore sizes are significantly small in lower micropore regions. The reported polymers also show moderate to high adsorption selectivity for CO2/N2 (40–78) and CO2/CH4 (5.7–7.8) as determined from the Ideal Adsorbed Solution Theory (IAST) calculation using pure gas isotherms at 298 K.

Highly porous and photoluminescent pyrene-quinoxaline-derived benzimidazole-linked polymers

Two highly porous and semiconducting pyrene-quinoxaline-derived benzimidazole-linked polymers have been synthesized and fully characterized. The polymers have a high surface area (SABET = ∼950 m2 g−1) while their electronic structure studies reveal bandgaps in the semiconducting range (2.02 and 2.16 eV) and emissions in the orange-red region (600 and 630 nm). The high surface area and optical properties make these polymers very interesting for gas storage, optoelectronics, and sensing applications.

Resonance Raman spectra of N-deprotonated σ-type dianion of porphycenes

Resonance Raman spectra of N-deprotonated sigma-type dianion of porphycenes were measured in an effort to characterize the structural changes concomitant with N-deprotonation. The observed resonance Raman behavior was consistent with the results of vibrational analysis by quantum chemical calculations based on density functional theory methods. Resonance Raman behavior predicted an expanded porphycene core for N-deprotonated sigma-type dianion with elongation of peripheral bond lengths. This sigma-type dianion is distinctive from pi-type dianion which has an expanded core with alternating changes in peripheral bond lengths.