Mesoporous Metal-Organic Frameworks with Exceptionally High Working Capacities for Adsorption Heat Transformation

Pore size is one of the most important parameters of adsorbents, and mesoporous materials have received intense attention for large guests. Here, a series of mesoporous coordination polymers underlying a new framework prototype for fast expansion of pore size is reported and the profound effect of pore size on adsorption heat transformation is demonstrated. Three isostructural honeycomb-like frameworks are designed and synthesized by combining ditopic linear metal oxalate chains and triangular tris-pyridine ligands. Changing the ligand bridging length from 5.5 to 8.6 and 9.9 Å gives rise to effective pore diameter from 20 to 33 and 37 Å, surface area from 2096 to 2630 and 2749 m² g^-1 , and pore volume from 1.19 to 1.93 and 2.36 cm³ g^-1 , respectively. By virtue of the unique and tunable isotherm shape of mesopores, exceptionally large working capacity up to 1.19 g g^-1 or 0.38 g cm^-3 for adsorption heat transformation can be achieved using R-134a (1,1,1,2-tetrafluroethane) as a working fluid.