Modular Functionalization of Metal‐Organic Frameworks for Nitrogen Recovery from Fresh Urine**

Abstract

Nitrogen recovery from wastewater represents a sustainable route to recycle reactive nitrogen (Nr). It can reduce the demand of producing Nr from the energy‐extensive Haber‐Bosch process and lower the risk of causing eutrophication simultaneously. In this aspect, source‐separated fresh urine is an ideal source for nitrogen recovery given its ubiquity and high nitrogen contents. However, current techniques for nitrogen recovery from fresh urine require high energy input and are of low efficiencies because the recovery target, urea, is a challenge to separate. In this work, we developed a novel fresh urine nitrogen recovery treatment process based on modular functionalized metal‐organic frameworks (MOFs). Specifically, we employed three distinct modification methods to MOF‐808 and developed robust functional materials for urea hydrolysis, ammonium adsorption, and ammonia monitoring. By integrating these functional materials into our newly developed nitrogen recovery treatment process, we achieved an average of 75% total nitrogen reduction and 45% nitrogen recovery with a 30 minutes treatment of synthetic fresh urine. The nitrogen recovery process developed in this work can serve as a sustainable and efficient nutrient management that is suitable for decentralized wastewater treatment. This work also provides a new perspective of implementing versatile advanced materials for water and wastewater treatment.

Molecule Engineering Metal–Organic Framework-Based Organic Photoelectrochemical Transistor Sensor for Ultrasensitive Bilirubin Detection

“…Functionalization-assisted structural modification confers MOFs diverse properties and gets more attention, and these materials have been applied in various fields such as gas storage and separation, catalysis, drug delivery, and sensors. − Precisely placing biomolecules or specific functional groups in highly ordered MOFs will help tailor the pore environment and broaden our understanding of the structure–activity relationship. For instance, without changing its original framework structure, urease covalently grafted MOF-808-U, oxalic acid-functionalized MOF-808-OA, and Cu-ion-doped MOF-808-Cu were designed for the conversion, capture, and recycling of nitrogen elements in urine . Wang et al reported that a tryptophan and histidine-treated amino-functionalized Cu-MOF mimics the behavior of natural oxidases by selectively capturing ascorbic acid from complex sweat components and effectively electro-oxidizing it, thus developing a highly sensitive sweat sensor .…”

“…For instance, without changing its original framework structure, urease covalently grafted MOF-808-U, oxalic acidfunctionalized MOF-808-OA, and Cu-ion-doped MOF-808-Cu were designed for the conversion, capture, and recycling of nitrogen elements in urine. 21 Wang et al reported that a tryptophan and histidine-treated amino-functionalized Cu-MOF mimics the behavior of natural oxidases by selectively capturing ascorbic acid from complex sweat components and effectively electro-oxidizing it, thus developing a highly sensitive sweat sensor. 22 In particular, the use of MOFs in biosensing applications with a specific recognition capability requires that further surface functionalization fulfills different detection tasks.…”