Saikat Das

Porous Organic Materials: Strategic Design and Structure–Function Correlation

Porous organic materials have garnered colossal interest with the scientific fraternity due to their excellent gas sorption performances, catalytic abilities, energy storage capacities, and other intriguing applications. This review encompasses the recent significant breakthroughs and the conventional functions and practices in the field of porous organic materials to find useful applications and imparts a comprehensive understanding of the strategic evolution of the design and synthetic approaches of porous organic materials with tunable characteristics. We present an exhaustive analysis of the design strategies with special emphasis on the topologies of crystalline and amorphous porous organic materials. In addition to elucidating the structure-function correlation and state-of-the-art applications of porous organic materials, we address the challenges and restrictions that prevent us from realizing porous organic materials with tailored structures and properties for useful applications.

Fabrication of COF-MOF Composite Membranes and Their Highly Selective Separation of H2/CO2

The search for new types of membrane materials has been of continuous interest in both academia and industry, given their importance in a plethora of applications, particularly for energy-efficient separation technology. In this contribution, we demonstrate for the first time that a metal-organic framework (MOF) can be grown on the covalent-organic framework (COF) membrane to fabricate COF-MOF composite membranes. The resultant COF-MOF composite membranes demonstrate higher separation selectivity of H2/CO2 gas mixtures than the individual COF and MOF membranes. A sound proof for the synergy between two porous materials is the fact that the COF-MOF composite membranes surpass the Robeson upper bound of polymer membranes for mixture separation of a H2/CO2 gas pair and are among the best gas separation MOF membranes reported thus far.

Standout electrochemical performance of SnO2 and Sn/SnO2 nanoparticles embedded in a KOH-activated carbonized porous aromatic framework (PAF-1) matrix as the anode for lithium-ion batteries

Attributed to their high specific capacity and safe working potential versus Li/Li+ as compared to commercial graphite anodes, tin and tin oxide have received widespread attention as promising anode materials for Li-ion batteries, whereas they also suffer from some drawbacks, such as large volume expansion and poor electrical conductivity during the lithiation/delithiation process. To address these issues, a series of composites with ultrasmall Sn and SnO2 nanoparticles (6–15 nm) embedded in a KOH-activated carbonized porous aromatic framework (PAF-1) matrix as anode materials were prepared by adjusting the Sn2+ content and carbonization temperature. Attributed to its high microporosity and electrical conductivity, the KOH-activated carbonized PAF-1 is a potential host matrix to cogently solve the problems of pulverization, metal aggregation and loss of electrical contact with the electrode over repeated cycling. The synergy between SnOx and the carbon matrix is manifested by the outstanding capacity and stability of the material, which owes its standout features to the SnOx nanoparticles located inside the micropores of the carbon matrix. Of all the materials, SnOx@K-PAF-1-750-25 prepared by optimizing the contents and preparation conditions showed excellent stability and cycling performance, retaining a capacity of 608 mA h g−1 over 400 charge/discharge cycles even at a high current density of 400 mA g−1.

Chiral Recognition and Separation by Chirality‐Enriched Metal–Organic Frameworks

Endowed with chiral channels and pores, chiral metal-organic frameworks (MOFs) are highly useful; however, their synthesis remains a challenge given that most chiral building blocks are expensive. Although MOFs with induced chirality have been reported to avoid this shortcoming, no study providing evidence for the ee value of such MOFs has yet been reported. We herein describe the first study on the efficiency of chiral induction in MOFs using inexpensive achiral building blocks and fully recoverable chiral dopants to control the handedness of racemic MOFs. This method yielded chirality-enriched MOFs with accessible pores. The ability of the materials to form host-guest complexes was probed with enantiomers of varying size and coordination and in solvents with varying polarity. Furthermore, mixed-matrix membranes (MMMs) composed of chirality-enriched MOF particles dispersed in a polymer matrix demonstrated a new route for chiral separation.

Charged porous organic frameworks bearing heteroatoms with enhanced isosteric enthalpies of gas adsorption

Charged porous organic frameworks containing heteroatoms were synthesized via a Yamamoto-type Ullmann coupling reaction using potassium tetrakis(4-bromopyrazolyl)borate and tetrakis(4-chlorophenyl)phosphonium bromide as monomers. For the first time, a monomer containing boron atoms was successfully homocoupled to obtain a 3D charged porous organic framework. The heteroatoms and charges in the porous organic frameworks help to increase the interaction between the frameworks and the gases. Therefore the charged porous organic frameworks bearing heteroatoms synthesized in the present study exhibit high isosteric enthalpies of gas adsorption which surpass those of many other porous organic materials.

Porous Organic Frameworks-derived Porous Carbons with Outstanding Gas Adsorption Performance

A series of porous carbon materials was synthesized via high temperature pyrolysis from well-defined and thermally stable precursors, namely porous organic frameworks(POFs), in inert atmosphere. The porous carbon materials showed enhanced gas adsorption capacities together with increased heat of adsorption and stronger affinity between the frameworks and the gases as compared to the precursor materials. To exemplify, sample C-POF-TBBP-1000 with a high BET surface area of 1290 m2/g can adsorb 2.8 mmol/g CH4(273 K, 101.325 kPa), 5.4 mmol/g CO2(273 K, 101.325 kPa) and 2.2% H2(mass fraction, 77 K, 101.325 kPa), thereby surpassing most other porous adsorbent materials reported till date. The study highlights the potential of porous carbons derived from novel porous organic framework structures for gas adsorption applications.