Dual-function 2D cobalt metal-organic framework embedded on paper as a point-of-care diagnostic device: Application for the quantification of glucose Haider A.J. Al Lawati * , Javad Hassanzadeh Department of Chemistry, College of Science, Sultan Qaboos University, Box 36, Al-Khod, 123, Oman highlights graphical abstract  Exceptional bifunctional activity of 2D cobalt metal-organic framework (CoMOF).  Notable enhancement of the stability and performance of GOX on the pa- per by CoMOF.  Superb catalyzing effect of CoMOF on the dissociation of H 2 O 2 to hydroxyl radicals.  Development of paper-based diag- nostic assay for glucose monitoring in blood.  Recording of colorimetric/fluoro- metric signals by smartphone readout. article info Article history: Received 10 April 2020 Received in revised form 10 September 2020 Accepted 11 September 2020 Available online 15 September 2020 Keywords: Bifunctional metal-organic frameworks Paper-based diagnostic device Smartphone Glucose abstract Point-of-care (POC) diagnostic devices play significant roles in delivering vital surveillance information and providing proper and timely care to patients. There is a challenge in the development of new diagnostic tools to overcome their current shortcomings in terms of cost issues, accuracy and perfor- mance. Herein, a highly efficient paper-based analytical device based on a 2D metal-organic framework (MOF) has been reported for the colorimetric/fluorometric monitoring of glucose. Because of the inherent bifunctional activity of cobalt-terephthalate MOF (CoMOF) nanosheets, great improvements were made to the stability and performance of glucose oxidase (GOX) and to its catalytic effect on the reaction of o-phenylenediamine (OPD) and H 2 O 2 . The exceptional behavior of 2D CoMOF, along with a precise smartphone readout, led to the rapid and sensitive colorimetric/fluorometric detection of glucose in biological samples. Paper modified by CoMOF and GOX was stable for a long time, and a yellow-brown color and a high fluorescence emission were observed after the addition of a low volume of sample and OPD solutions. The probe showed a wide linear effectiveness range of 50 mM-15 mM, with colorimetric and fluorometric detection limits of 16.3 and 3.2 mM, respectively. Despite its great simplicity, the developed probe showed high performance and accuracy for the quantification of glucose. © 2020 Elsevier B.V. All rights reserved. 1. Introduction The increased risk of epidemic or chronic diseases and high cost * Corresponding author. E-mail address: haiderl@squ.edu.om (H.A.J. Al Lawati). Contents lists available at ScienceDirect Analytica Chimica Acta journal homepage: www.elsevier.com/locate/aca https://doi.org/10.1016/j.aca.2020.09.026 0003-2670/© 2020 Elsevier B.V. All rights reserved. Analytica Chimica Acta 1139 (2020) 15e26