Porous liquids (PLs) are pure liquids and mixtures with permanent internal porosity for gas capture. Notably, PLs have demonstrated emergent gas adsorption and selectivity exceeding the weighted average of the individual PL constituents. To date, PL materials design has primarily leveraged broad heuristics to discover novel PL compositions. For example, previous studies have targeted PLs composed of sorbents suspended in large, bulky solvents that cannot diffuse though their static pore windows. Some recent computational studies have explored the impact of solvent on the stability and gas separation potential of PL compositions. Here, we use atomically detailed molecular dynamics simulations to explore the design space of sorbent surface chemistry for novel PLs with enhanced CO2 sorption. ZIF-8 was selected as a model nanoporous host due to its stability in solution, tunability, and high CO2 selectivity for capture from dilute gas streams. The surface chemistry of ZIF-8 (zeolitic imidazolate framework 8) was tuned by substituting surface-exposed 2-methylimidazole (mIm) for 3-amino-1,2,4-triazole (Atz) to produce a variety of surface functionalization schemes with CO2 adsorption increases with higher fractions of Atz functionalization. The structure of solvent at the sorbent interface reveals that optimal ZIF-8 functionalization schemes tend to reduce solvent infiltration and hence enhance CO2 uptake. This novel in silico approach to PL design enables an accelerated discover timeline and molecularly informed design rules for PLs with emergent gas separation capabilities. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
