New‐Generation Anion‐Pillared Metal–Organic Frameworks with Customized Cages for Highly Efficient CO₂ Capture

Abstract

The rational design of porous materials for CO 2 capture under realistic process conditions is highly desirable. However, trade-offs exist among a nanopore's capacity, selectivity, adsorption heat, and stability. In this study, a new generation of anion-pillared metal-organic frameworks (MOFs) are reported with customizable cages for benchmark CO 2 capture from flue gas. The optimally designed TIFSIX-Cu-TPA exhibits a high CO 2 capacity, excellent CO 2 /N 2 selectivity, high thermal stability, and chemical stability in acid solution and acidic atmosphere, as well as modest adsorption heat for facile regeneration. Additionally, the practical separation performance of the synthesized MOFs is demonstrated by breakthrough experiments under various process conditions. A highly selective separation is achieved at 298-348 K with the impressive CO 2 capacity of 2.1-1.4 mmol g −1 . Importantly, the outstanding performance is sustained under high humidity and over ten repeat process cycles. The molecular mechanism of MOF's CO 2 adsorption is further investigated in situ by CO 2 dosed single crystal structure and theoretical calculations, highlighting two separate binding sites for CO 2 in small and large cages featured with high CO 2 selectivity and loading, respectively. The simultaneous adsorption of CO 2 inside these two types of interconnected cages accounts for the high performance of these newly designed anionic pillar-caged MOFs.

Trace SO2 Gas Capture in Stable 3D Viologen Ionic Porous Organic Framework Microsphere

“…The emission of the toxic gas sulfur dioxide (SO 2 ) from fossil fuel combustion represents one of the most serious pollutions that threaten human health. − The components of typical flue gas mainly include 10–12% CO 2 , 500–3000 ppm SO 2 , and 40 ppm NO 2 . − Conventional flue gas desulfurization (FGD) process with limestone can remove about 90–95% of SO 2 , but the residual SO 2 (about 400 ppm) still significantly inactivates CO 2 -capturing adsorbents or absorbents. − Developing reversible physisorption technologies derived from porous materials for trace SO 2 removal could be a possibility in view of process economy and energy efficiency. − Many porous materials such as zeolites, COFs (covalent organic frameworks), MOFs (metal organic frameworks), and POFs (porous organic frameworks)­have been evaluated as SO 2 adsorbents. − Particularly, ionic porous materials enriched with high-density anions sites have attracted more attention due to their superior separation performance. ,,− …”

Highly Efficient CO2 Capture from Wet–Hot Flue Gas by a Robust Trap-and-Flow Crystal

“…Based on the actual capture of CO 2 in flue gas, six criteria need to be carefully considered: suitable CO 2 adsorption capacity (0.15 bar), 333–363 K (>0.8 mmol/g), high selectivity with main component (CO 2 /N 2 : >2000), good thermal stability (>523 K), excellent chemical stability (in acid or basic aqueous solution of 363 K), moderate isosteric heat of adsorption (<40 kJ/mol), and low price of the ligand (<40 $/kg). , Particularly, CO 2 uptake at 0.15 bar and 363 K of NTU-67 (0.872 mmol/g) is higher than the classic stable PCPs (ZIF-8: 0.075 mmol/g, UiO-66: 0.120 mmol/g, MIL-101 (Cr): 0.067 mmol/g, SIFSIX-1-Cu: 0.096 mmol/g) and CALF-20: 0.750 mmol/g with moderate Q st (<40 kJ/mol) Table S2. In addition, NTU-67 features good adsorption selectivities of CO 2 /N 2 (2424), CO 2 /O 2 (211), and CO 2 /CO (70).…”

“…Commonly, the one-dimensional (1D) straight channel dominated by kinetics was developed for CO 2 adsorption. , It is also stated that the crystal with ink-bottle-like cavity projects high surface areas and high pore volumes for accommodating more gas molecules. However, the narrow and singular tandem channels urge the competitive bump, causing slow diffusion or high binding energy. − Notably, compared with the tandem-arrayed channel, the orthogonal-arrayed dynamic molecular pocket is a promising design to achieve rapid kinetic diffusion and molecular accommodation, but such local dynamic may be influenced by water molecules, and even worse under hot conditions. Notably, the shunt flow-and-trap pore system for multiple passages with independent function provides an opportunity for simultaneously rapid diffusion and appropriate adsorption for CO 2 molecules, as well as the rejection of water molecules by defined window aperture (Scheme ).…”

A process-level perspective of the impact of molecular force fields on the computational screening of MOFs for carbon capture

“…This data was obtained using a HTCS workflow that has been developed 56 and validated elsewhere. 57,58 For more technical details on the GCMC simulations, see the ESI, † supplementary note 1.…”