Immobilization of Lewis Basic Nitrogen Sites into a Chemically Stable Metal–Organic Framework for Benchmark Water‐Sorption‐Driven Heat Allocations

Abstract

Abstract Developing efficient and stable water adsorbents for adsorption‐driven heat transfer technology still remains a challenge due to the lack of efficient strategies to enhance low‐pressure water uptakes. The authors herein demonstrate that the immobilization of Lewis basic nitrogen sites into metal–organic frameworks (MOFs) can improve water uptake and target benchmark coefficient of performances (COPs) for cooling and heating. They present the water sorption properties of a chemically stable MOF (termed as Zr‐adip), designed by incorporating hydrophilic nitrogen sites into the adsorbent MIP‐200. Zr‐adip exhibits S‐shaped sorption isotherms with an extremely high water uptake of 0.43 g g−1 at 303 K and P/P0 = 0.25, higher than MIP‐200 (0.39 g g−1), KMF‐1 (0.39 g g−1) and MOF‐303 (0.38 g g−1). Theoretical calculations reveal that the incorporated N sites can serve as secondary adsorption sites to moderately interact with water, providing more binding sites to strengthen the water binding affinity. Zr‐adip achieves exceptionally high COPs of 0.79 (cooling) and 1.75 (heating) with a low driving temperature of 70 °C, outperforming MIP‐200 (0.78 and 1.53) and KMF‐1 (0.75 and 1.74). Combined with its ultrahigh stability, excellent cycling performance, and easy regeneration, Zr‐adip represents one of the best water adsorbents for adsorption‐driven cooling and heating.

Keywords

• chillers
• coefficient of performances
• heat pump
• porous materials
• water adsorption