Ketone-Functionalized Covalent Organic Frameworks for Ambient-Temperature Hydrogen Storage: Pore Engineering, Adsorption Thermodynamics, and Volumetric Capacity Optimization

This study investigates ketone-functionalization strategy for covalent organic framework pore walls to enhance hydrogen binding enthalpy and ambient-temperature gravimetric and volumetric storage capacity within the context of materials chemistry and porous materials engineering, an area of growing scientific importance given its implications for on-board hydrogen vehicle storage, stationary hydrogen buffer storage, and MOF/COF materials discovery for hydrogen economy infrastructure. Using solvothermal COF synthesis with PXRD and N2 BET pore characterization, hydrogen adsorption isotherms at 77 K and 298 K, and Grand Canonical Monte Carlo simulation with DFT-fitted force fields, we examine ketone oxygen lone pairs interacting with H2 quadrupole moment via electrostatic polarization increasing isosteric heat of adsorption from 5-6 kJ/mol to 8-10 kJ/mol, shifting operating conditions toward ambient temperature for practical gravimetric capacity in 12 COF variants (4 pore diameters x 3 ketone loadings) characterized by BET, PXRD, and volumetric hydrogen adsorption at 77 K, 195 K, and 298 K at pressures 0-100 bar drawn from solvothermal synthesis in dioxane:acetic acid at 120 C, characterized by Rigaku MiniFlex PXRD and Quantachrome Autosorb iQ-XR volumetric adsorption. Results indicate that di-ketone COF with 24-A pore diameter achieves 2.84 wt% and 28.4 g/L H2 at 298 K/100 bar with isosteric heat 9.2 kJ/mol, representing a 2.4-fold ambient-temperature capacity improvement over unfunctionalized parent framework (p < 0.001), with 2.84 wt% H2 at 298 K/100 bar; 2.4x improvement over unfunctionalized; Qst 9.2 kJ/mol as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to materials chemistry and porous materials engineering and carry actionable implications for the design of programs and policies targeting on-board hydrogen vehicle storage, stationary hydrogen buffer storage, and MOF/COF materials discovery for hydrogen economy infrastructure.