Accurate forecasting of air quality is critical, as PM \(_{2.5}\) pollution poses serious risks to environmental sustainability and public health. This study proposes a novel hybrid deep ensemble framework integrating CNN, BiLSTM, and GRU within a stacked architecture, with a Gradient Boosting Machine (GBM) serving as the meta-learner. Using daily PM \(_{2.5}\) data from Delhi, India, the framework is benchmarked against classical and deep learning models. Results demonstrate that the hybrid ensemble consistently outperforms baselines, achieving MAE of 8.09, RMSE of 10.70, and R \(^{2}\) of 0.96, representing a 27.80% improvement in predictive correlation over the cutting-edge hybrid BiLSTM–GRU model. These findings highlight the effectiveness of ensemble learning in modeling complex pollution dynamics and underscore the potential of the proposed framework as a reliable decision-support tool for policymakers and urban planners.