Computational Screening And Performance Study Of Metal-Organic Frameworks For Gas Separation

The rapid development of chemical industry constantly puts forward new requirements for chemical separation technology.As an alternative to traditional energy-intensive separation technologies,energy-saving and efficient adsorption separation technology has attracted more and more attentions.Recently,novel metal-organic frameworks（MOFs）have shown great application potential in the field of gas separation due to their high specific surface area and structural diversity.However,the structural diversity of MOFs also brings difficulties for the on-demand development of materials only by experimental method.Therefore,this work introduces high-throughput computational screening technology combined with experimental methods to carry out a series of studies on the capture and removal of pollution gases（SF₆/N₂and SO₂/CO₂）and the separation and purification of resource gases（D₂/H₂and C₃H₈/C₃H₆）in MOFs as followed:（1）Finding optimal adsorbents to achieve an efficient capture and recovery of SF₆from SF₆/N₂mixture is of great industrial importance.To address this key challenge,a materials-genomics-accelerated strategy was proposed to develop promising materials by combining high-throughput computational screening with subsequent synthesis and adsorption/separation testing.From over 10000 MOFs,those with calixarene-analogous pore feature were computationally identified as optimal adsorbents with exceptional SF₆/N₂selectivity and SF₆uptake.As a proof-of-concept,one of the discovered MOFs Cu-MOF-NH₂was further synthesized.Equilibrium adsorption measurements demonstrated that Cu-MOF-NH₂exhibated both high SF₆adsorption capacity as a single component at 0.1 bar(3.39 mmol g^-1)and SF₆/N₂selectivity（～266）under ambient conditions.Dynamic breakthrough experiments further confirmed the attractiveness of this MOF for SF₆capture under working conditions,excellent regeneration and cycling performance.The separation mechanism was revealed to be thermodynamically driven owing to the synergistic contribution of multiple hydrogen-bond and van der Waals-type SF₆/MOF pore wall interactions.（2）Adsorptive removal of SO₂from its low-concentrated gas mixtures is significant to the health and environment.However,the on-demand discovery of such adsorbents remains a great challenge.Herein,a high-throughput computational screening for SO₂/CO₂separation is performed in an anion-pillared metal-organic framework（APMOF）database.As a proof-of-concept,SIFSIX-7-Cu,one of the computationally top-ranked MOFs,is identified and experimentally synthesized for the verification.The high SO₂uptake(14.7 mmol g^-1),selectivity（120 for a mixture of 0.2/99.8 molar ratio）and excellent balance between the regenerability（63.5%）and adsorbent performance score（36.3）make it superior to the performance of most reported adsorbents.This work not only provides an excellent candidate for SO₂/CO₂separation,but also will facilitate the development of theoretical prediction-experimental verification methodology in the discovery of novel materials.（3）D₂is a key energy source for fusion reaction and been widely used in various application fields.Nevertheless,the separation of D₂from its isotopic mixture with nearly same physicochemical properties is one of the greatest challenging tasks in industry.Compared with cryogenic distillation technology,quantum sieving effect based on nanoporous materials has been proposed as a promising strategy for isotopes separation,in which MOFs are considered as an ideal platform because of their structural diversity and tailorable functionality.In this work,high-throughput molecular simulations were performed to identify optimal structural features of high-performance materials from a recently-constructed database of APMOF.As a proof-of-concept,the identified material SIFSIX-18-Cd was prepared using a proposed direct mixing method,which can achieve a goal of quickly preparation of such material on a large scale.The experimental pure-component adsorption isotherms of D₂and H₂confirmed the preferential adsorption of SIFSIX-18-Cd for D₂over H₂due to the quantum sieving effect.The advanced cryogenic thermal desorption spectroscopy（ACTDS）measurements further showed that the enrichment factor（EF）of an equimolar D₂/H₂mixture in SIFSIX-18-Cd can reach 5.1 at 30 K and 1.0 bar,which is higher than the current cryogenic distillation method（1.5 at 24 K）.Along with the proposed efficient preparation method,the high hydrophobic property of SIFSIX-18-Cd also demonstrated a broad industrial prospect of this material for hydrogen isotope separation.（4）It is an extremely challenging task to capture C₃H₈from the C₃H₈/C₃H₆mixture,which requires an adsorbent with a specific pore structure.Herein,a large database of hypothetical multivariate MOF（MTV-MOF）composed of>10000 materials is screened for C₃H₈/C₃H₆separation using high-throughput simualtions under ambient conditions.Firstly,the relationship between the structural and chemical characteristics of MTV-MOF and C₃H₈/C₃H₆separation performance was studied.It was found that the material exhibited the highest C₃H₈/C₃H₆selectivity when LCD was in the range of 6-7?,ASA was in the range of 1500-2000 m²g^-1,V_porewas in the range of 0.7-0.8cm³g^-1andφwas in the range of 0.55-0.65.In addition,the highest average selectivity of materials can be observed in which constructed with functional group 11（F-F）modified ligands.Based on a combination of selectivity,capacity,APS and R%,the high performance candidate p MOF＿376 was identified.Notably,the ligands used to construct p MOF＿376 is a combination of 14N/18C/12C which is not modified by functional groups.The theoretical calculations found that the two“COO”ligands can stronger trapped C₃H₈due to the multiple cooperative van der Waals interactions which dominated by dispersion forces.