ground states (S 0 ). Owing to the spin-forbidden situation between singlet (S 1 ) and triplet excitation transitions and the nonradiative decay process by molecular vibration and rotation, rigorous conditions are essential to achieve RTP. [15,16] The strategies of designing RTP molecular structures can be divided into two aspects. One is to make use of heteroatoms, such as N or P, to reinforce the spin-orbit coupling for promoting the intersystem crossing (ISC). The other is the introduction of rigid matrix or cross-linking to suppress nonradiative transitions of triplet excitations. [17,18] Currently, polymer-based phosphorescent materials gain more and more important attention because of the low cost and facile preparation process as well as favorable biocompatibility compared with metal-containing materials. [19] The polymers showing RTP are usually based on their solid-state phase without water, since the dissolved oxygen in water may quench the phosphorescence. [20][21][22][23] Only a few phosphorescent systems in aqueous conditions have been reported. [22,[24][25][26][27] In these studies, the noncovalent bonding strategies such as hydrogen bonding formations [22,24] and electrostatic interactions [27] have been developed to suppress the nonradiative transition of phosphorescent molecules in order to realize RTP. [25] For the electrostatic interactions, phosphorescent molecules are usually introduced into the electrostatic matrix to obtain luminescent materials with RTP properties. Because of the noncovalent bonding nature, the stability of these materials could be easily affected by external conditions. [8] Thus, straightforward preparation of the RTP materials through covalently cross-linked networks is still desirable.Click chemistry possesses essential advantages that could be employed for polymer synthesis, including mild reaction conditions, fast reaction rate, easy purification, as well as being friendly with water, oxygen, and structurally complicated reactants. [28][29][30][31] Based on previous studies, a rigid structure can be formed by substituting boronic acid with a polymer that contains a hydroxyl group per monomer through BO click reaction. [32] Significantly, the BO covalent bond can be actualized under an ambient environment without a complicated Ultralong room temperature phosphorescence is employed in information encryption, chemical sensing, lighting, and imaging on account of its long lifetime and high signal-to-noise ratio. As the triplet excitons can be easily quenched and interfered by nonradiative transition process, it is difficult to obtain long-lived phosphorescence through conventional methods. Herein, a general design strategy to form cross-linked networks by click chemistry is presented for efficiently promoting the phosphorescence performance. Using the hydrogen bonding interactions formed between CO•••HN units and covalently cross-linked network by the BO bond, the rigidity of the entire system is greatly enhanced, so the radiative transition process is well strengthe...
