Development of Adsorbents for Selective Carbon Capture: Role of Homo- and Cross-Coupling in Conjugated Microporous Polymers and Their Carbonized Derivatives

Selective adsorption of CO₂ from natural gas results in increased calorific value, decreased gas volume, and reduced corrosion. For this purpose, the development of high-performance adsorbents with regard to both adsorption capacity and CO₂/CH₄ selectivity receives great attention. Herein, two new conjugated microporous polymers (CMPs) were prepared by Yamamoto homocoupling and Sonogashira-Hagihara cross-coupling reaction. The significant role of homo- and cross-coupling in CMPs in selective CO₂ separation was investigated. Notably, the cross-coupled CMP (NUT-15, NUT means Nanjing Tech University) shows CO₂ uptake around twice that of homocoupled CMP (NUT-14) under the analogous conditions. Furthermore, the importance of KOH-activation and temperature-controlled carbonization in efficient CO₂ capture was studied. For this, NUT-15 was further subjected to carbonization and highly active porous carbons (PCs) were obtained. It is noteworthy that PC-800 with high carbonization yield (78%) and suitable pore structure demonstrates excellent CO₂ uptake (5.4 mmol·g^-1) and selectivity (22.0) over CH₄ at 273 K and 1 bar. Such CO₂ uptake is higher than those of some benchmarks including activated carbon (2.8 mmol·g^-1), PTz4 (3.6 mmol·g^-1), and UTSA-50a (4.6 mmol·g^-1) at 273 K and 1 bar. The high production yield, excellent CO₂ uptake, and high selectivity make the present PCs promising candidates for selective CO₂ separation from natural gas.