In the context of the evolving digital era, this study introduces a conceptual model that integrates Education for Sustainable Development (ESD) into English for Academic Purposes (EAP) writing, leveraging Critical Digital Literacies (CDL). It aims to develop EFL doctoral students' competencies necessary for sustainable development, addressing the gap in current genre-based EAP instruction that often neglects comprehensive ESD competencies such as systems thinking and self-awareness. Utilizing innovative tools like ChatGPT within a CDL framework, the model focuses on both explicit teaching objectives related to genre knowledge and implicit ones tied to ESD. Specifically, the study outlines eight scenarios where GPT technology aids in achieving these pedagogical goals. By implementing this model, we aim not only to enrich the EAP writing curriculum but also to subtly shift educational practices towards embracing the values of sustainability and digitalization.