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1.
ACS Appl Mater Interfaces ; 16(17): 22066-22078, 2024 May 01.
Article in English | MEDLINE | ID: mdl-38629710

ABSTRACT

Development of crystalline porous materials for selective CO2 adsorption and storage is in high demand to boost the carbon capture and storage (CCS) technology. In this regard, we have developed a ß-keto enamine-based covalent organic framework (VM-COF) via the Schiff base polycondensation technique. The as-synthesized VM-COF exhibited excellent thermal and chemical stability along with a very high surface area (1258 m2 g-1) and a high CO2 adsorption capacity (3.58 mmol g-1) at room temperature (298 K). The CO2/CH4 and CO2/H2 selectivities by the IAST method were calculated to be 10.9 and 881.7, respectively, which were further experimentally supported by breakthrough analysis. Moreover, theoretical investigations revealed that the carbonyl-rich sites in a polymeric backbone have higher CO2 binding affinity along with very high binding energy (-39.44 KJ mol-1) compared to other aromatic carbon-rich sites. Intrigued by the best CO2 adsorption capacity and high CO2 selectivity, we have utilized the VM-COF for biogas purification produced by the biofermentation of municipal waste. Compared with the commercially available activated carbon, VM-COF exhibited much better purification ability. This opens up a new opportunity for the creation of functionalized nanoporous materials for the large-scale purification of waste-generated biogases to address the challenges associated with energy and the environment.

2.
Inorg Chem ; 63(13): 6092-6102, 2024 Apr 01.
Article in English | MEDLINE | ID: mdl-38507817

ABSTRACT

In this work, we illustrated the design and development of a metal-coordinated porous organic polymer (POP) namely VO@TPA-POP via a post-synthetic metalation strategy to incorporate oxo-vanadium sites in a pristine polymer (TPA-POP) having acetylacetonate (acac) as anchoring moiety. The as-synthesized VO@TPA-POP exhibited highly robust and porous framework, which has been utilized for thioanisole (TA) oxidation to its corresponding sulfoxide. The catalyst demonstrated notable stability and recyclability by maintaining its catalytic activity over multiple reaction cycles without any significant loss in activity. The X-ray absorption spectroscopy (XAS) and density functional theory (DFT) analysis establish the existence of V(+4) oxidation state along with the VO(O)4 active sites into the porous network and the most energetically feasible mechanistic pathway involved in the TA oxidation, respectively, indicating the role of electron density associated with vanadium center during the catalytic transformation. Thus, this work aims at the demonstration of versatility and potential of VO@TPA-POP as a porous heterogeneous catalyst for the TA oxidation followed by decontamination of sulfur mustards (HD's) to their corresponding less toxic sulfoxides in a more efficient and greener way.

3.
Angew Chem Int Ed Engl ; 62(50): e202311304, 2023 Dec 11.
Article in English | MEDLINE | ID: mdl-37872849

ABSTRACT

Herein, we have specifically designed two metalated porous organic polymers (Zn-POP and Co-POP) for syngas (CO+H2 ) production from gaseous CO2 . The variable H2 /CO ratio of syngas with the highest efficiency was produced in water medium (without an organic hole scavenger and photosensitizer) by utilizing the basic principle of Lewis acid/base chemistry. Also, we observed the formation of entirely different major products during photocatalytic CO2 reduction and water splitting with the help of the two catalysts, where CO (145.65 µmol g-1 h-1 ) and H2 (434.7 µmol g-1 h-1 ) production were preferentially obtained over Co-POP & Zn-POP, respectively. The higher electron density/better Lewis basic nature of Co-POP was investigated further using XPS, XANES, and NH3 -TPD studies, which considerably improve CO2 activation capacity. Moreover, the structure-activity relationship was confirmed via in situ DRIFTS and DFT studies, which demonstrated the formation of COOH* intermediate along with the thermodynamic feasibility of CO2 reduction over Co-POP while water splitting occurred preferentially over Zn-POP.

4.
Chem Asian J ; 18(1): e202200970, 2023 Jan 03.
Article in English | MEDLINE | ID: mdl-36373678

ABSTRACT

Herein, we have designed and synthesized two heteroatom (N, O) rich covalent organic frameworks (COF), PD-COF and TF-COF, respectively, to demonstrate their relative effect on CO2 adsorption capacity and also CO2 /N2 selectivity. Compared to the non-fluorinated PD-COF (BET surface area 805 m2 g-1 , total pore volume 0.3647 ccg-1 ), a decrease in BET surface area and also pore volume have been observed for fluorinated TF-COF due to the incorporation of fluorine to the porous framework (BET surface area 451 m2 g-1 , total pore volume 0.2978 ccg-1 ). This fact leads to an enormous decrease in the CO2 adsorption capacity and CO2 /N2 selectivity of TF-COF, though it shows stronger affinity towards CO2 with a Qst of 37.76 KJ/mol. The more CO2 adsorption capacity by PD-COF can be attributed to the large specific surface area with considerable amount of micropore volume compared to the TF-COF. Further, PD-COF exhibited CO2 /N2 selectivity of 16.8, higher than that of TF-COF (CO2 /N2 selectivity 13.4).

5.
ACS Appl Mater Interfaces ; 14(1): 771-783, 2022 Jan 12.
Article in English | MEDLINE | ID: mdl-34962379

ABSTRACT

The main component of natural gas is methane, whose combustion contributes to global warming. As such, sustainable, energy-efficient, nonfossil-based methane production is needed to satisfy current energy demands and chemical feedstocks. In this article, we have constructed a metal-free porous polyketone (TPA-DPA PPK) with donor-acceptor (D-A) groups with an extensive π-conjugation by facile Friedel-Crafts acylation reaction between triphenylamine (TPA) and pyridine-2,6-dicarbonyl dichloride (DPA). TPA-DPA PPK is a metal-free catalyst for visible-light-driven CO2 photoreduction to CH4, which can be used as a solar fuel in the absence of any cocatalyst and sacrificial agent. CH4 production (152.65 ppm g-1) is ∼5 times greater than that of g-C3N4 under the same test conditions. Charge-density difference plots from excited-state time-dependent density functional theory (TD-DFT) calculations indicate a depletion and accumulation of charge density among the donor/acceptor functional groups upon photoexcitation. Most notably, binding energies from DFT demonstrate that H2O is more strongly bound with the pyridinic nitrogen group than CO2, which shed insight into mechanistic pathways for photocatalytic CO2 reduction.

6.
Chem Commun (Camb) ; 57(69): 8550-8567, 2021 Sep 07.
Article in English | MEDLINE | ID: mdl-34369958

ABSTRACT

Porous organic polymers (POPs) represent an emerging class of porous organic materials which mainly comprise organic building blocks that are interconnected via strong covalent bonds, thereby offering highly cross-linked frameworks with rigid structures and specific void spaces for accommodating guest molecules. In the past few years, POPs have garnered colossal research interest as nanoreactors for heterogeneous catalysis (thermal, photochemical, electrochemical, etc.) because of their intriguing characteristic features, such as high thermal and chemical stabilities, adjustable chemical functionalities, large surface areas, and tunable pore size distributions. This feature article provides an overview of existing research relating to diverse POP synthetic approaches (COFs, CTFs, and some amorphous POPs), the possible modification of the functionality of POPs, and their exciting application as next-generation nanoreactors. These POPs are extremely interesting, as they offer the potential for either metal-free or metalated polymer catalysts allowing photocatalytic CO2 reduction to solar-fuel, biofuel upgrades, the conversion of waste cooking oil to bio-oil, and clean H2 production from water, addressing many scientific and technological challenges and providing new opportunities for various specific topics in catalysis. Finally, we emphasize that the integration of various synthetic approaches and the application of POPs as nanoreactors will provide opportunities in the near future for the precision synthesis of functional materials with significant impact in both basic and applied research areas.


Subject(s)
Metal-Organic Frameworks/chemistry , Catalysis , Metal-Organic Frameworks/chemical synthesis , Porosity
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